By Phil Mattingly and Lauren Fox, CNN

(CNN) -- Senate Republicans, in less than 72 hours, have put themselves on the path to confirm a nominee to dramatically shift the balance of power in the US Supreme Court. And they very well may do it before the November 3 election.

Bottom line

There is no on-ramp or slow lead-up to what's happening at this moment, in the middle of an increasingly divisive election taking place in a fractured country. A colossal battle, the contours of which have been laid over years of judicial fights, disputes and wars, was under way within hours of the death of Ruth Bader Ginsburg. Republicans have grown more and more confident they can confirm the liberal icon's successor in the weeks ahead, according to senators and senior aides. But how -- and when -- is still coming together.

What to watch today

-Senate GOP closed-door leadership meeting, 5 p.m. ET

-Senate vote -- and first opportunity to talk to rank-and-file senators -- 5:30 p.m.

Days until the election

43

The reversal

Republicans have had no issue doing a complete 180-degree shift on their 2016 position on holding open a seat in an election year. Officially, it's because the circumstances are different -- unlike 2016, the White House and Senate are controlled by the same party.

The reality is this is just a raw power play. Republicans have the power. They're going to exert that power, and no amount of video clips or old quotes that seemingly make them appear to be hypocrites will change that, according to more than a dozen senators and top aides to whom we spoke over the weekend.

"They'd do the same thing," a GOP senator told me, rationalizing the turnabout. (See more on this in Sen. Lamar Alexander's statement below.)

The math

Senate Majority Leader Mitch McConnell can lose three Republicans if this vote is held before election day, because Vice President Mike Pence can cast a potential tie-breaking vote. McConnell has already lost two -- Sens. Susan Collins of Maine and Lisa Murkowski of Alaska. But finding another two Republican lawmakers who are going to defy their leader on an issue that is as core to Republican orthodoxy as the highest court, that's tough.

All eyes had been on Alexander. He was retiring. He's a Senate institutionalist. But, he's also a close ally of McConnell's and a reliable GOP vote. Alexander coming out in full support of McConnell's strategy made it hard to imagine who the fourth member would be.

The timeline

McConnell, whose career work has been defined by filling the courts with conservative judges, had a single message for his 52 GOP Senate colleagues Friday night: "keep your powder dry." That, of course, was only the message if any members were considering calling for Republicans to hold off on confirming Ginsburg's successor. For those ready to move -- and move quickly -- McConnell welcomed their public comments. They've served the purpose of creating momentum, and in these cases, momentum can drive everything, including how fast the process moves along.

The actual vote

McConnell hasn't said if a vote will happen before or after the election. And, he may not have to decide tomorrow, this week or even this month. It's possible Republicans start down this road, get a nominee, hold hearings and debate without a public pronouncement of when a vote will actually take place. That gives campaigns time to poll and McConnell more time to win over his conference. It also is a fact that predicting a timeline this early in the game isn't necessary or even practical. Need proof? See the nomination of Brett Kavanaugh.

Expect a lot of responses from GOP senators like this when we ask them about timing

"This should take as long as it needs to take, but no longer," Sen. Roy Blunt, a Republican from Missouri, told CBS Sunday. "There is plenty of time to get this done, but to get this done before Election Day, everything has to work pretty precisely."

The case for a pre-election vote

This weekend, conservative senators publicly deployed their campaign to convince McConnell and President Donald Trump to hold a vote on a Supreme Court nominee before the election. There's a reason for that. And, there is a reason that McConnell might consider it even if we are just more than 40 days away from the election.

Every moment spent on the Supreme Court is a moment when voters aren't talking about a massive pandemic that has overwhelmed the country's health care facilities, eroded the economy, and taken the lives of nearly 200,000 Americans. This election was going to be a referendum on Trump. Now, it's a reminder for conservatives and the Republican base about what is at stake: the courts.

Conservatives want to move on the court now because things can always change after the election. Trump could lose, the Senate could flip or the fight for the WH could become so close, so contentious and disputed that the court will play a pivotal role. They want it filled with nine justices -- three of whom were selected by Trump -- if that happens.

Something to keep in mind

A good adage for leaders on Capitol Hill that rarely fails: If you have the votes, you vote. McConnell is on the cusp of having the green light to put a process in motion that would lead to a confirmation vote before the election. It doesn't mean he will, but the talk of this being destined for the lame duck is far from a sure thing, according to people with knowledge of the process. In fact, Republicans are growing more and more comfortable with a vote before the election, those people say.

Another key point

The selection belongs to Trump. The process belongs to McConnell. In other words -- if McConnell says it, that's what's going to happen. If you hear it from someone else, best to wait for McConnell to confirm it before you consider it Gospel.

Who to watch

Sen. Cory Gardner

Since coming to Washington six years ago, Gardner has rarely defied his party. He did get into a battle with the former Attorney General Jeff Sessions on marijuana a few years ago, but Gardner isn't a senator who steps outside the GOP tent very often. Now, however, he is arguably the most vulnerable Republican up for reelection in a state that looks very different from what it did six years ago. If there was ever a time for Gardner to say no to McConnell and the President, this would be it. But, as much as a vote for Trump's SCOTUS nominee could hurt Gardner with Democrats, voting against it or advertising you aren't comfortable moving before the election will hurt Gardner with his base. When you are in a razor-thin reelection fight, you can't risk cratering support from the people who were going to vote for you for people who are likely to vote for your opponent.

Sen. Mitt Romney

Romney's reputation, at least in this early stage of his Senate career, is to cross the aisle on crucial and controversial votes. He proved that last winter during impeachment when he voted with Democrats on one article. But Romney is also deeply conservative. And, when it comes to votes backing Republican values, he's not typically one to abandon the party. The key question with Romney at this point is does he see this as a vote about fairness? A vote about playing by the rules McConnell established when Barack Obama was President and Republicans refused to hold hearings or a vote on Merrick Garland. Or does he view this as a moment of consequence for conservative values and sticks with the team?

The statement to read

Alexander, the senior senator from Tennessee who is respected on both sides of the aisle and carries the institutionalist mantle, was considered a possible wild card when this first started. He is not. And his explanation as to why is worth reading, as it is probably the best rationale anyone has given for why Republicans are so quickly coalescing behind moving forward -- and fast.

"No one should be surprised that a Republican Senate majority would vote on a Republican President's Supreme Court nomination, even during a presidential election year. The Constitution gives senators the power to do it. The voters who elected them expect it. Going back to George Washington, the Senate has confirmed many nominees to the Supreme Court during a presidential election year. It has refused to confirm several when the President and Senate majority were of different parties. Senator McConnell is only doing what Democrat leaders have said they would do if the shoe were on the other foot."

A couple points here: the first goes to the raw power view of things. Republicans control the chamber. The Senate's job is to advise and consent (or not). The majority has full authority to decide which of those paths it chooses, no matter if the rationale is seen as hypocritical or based on some made up rule (seriously, the "Biden rule" is not a thing).

Second is the final sentence in Alexander's statement. Nothing defines the judicial wars of the last 15 years like the idea that any action was only taken because if it weren't, the other side certainly would if put in the same position. Alexander, who is traditionally one of the more bipartisan senators in the chamber, underscores just how little of that exists on judges -- or really on anything at this point.

On McConnell

There has been no shortage of psychoanalysis of the Kentucky Republican over the years, and there will certainly be reams of it to come in the days ahead. This won't be that, but just a couple of quick points to keep in mind in the weeks ahead:

McConnell's life-long political passion has been the judiciary. This confirmation would create the most conservative court in nine decades. If there's one thing he will figure out a way to do, it's fill this seat.

The threats of Democrats adding seats to the Supreme Court, or doing away with the filibuster, or any number of potential retaliatory options should the seat be filled, have no bearing on him. As one adviser said this weekend, given the threat to do away with the filibuster has been on Democratic minds for months: "They already shot that hostage."

The most interesting element, by far, of this process will become if the political interests of his conference and the ability to confirm Ginsburg's replacement diverge. It's not clear they will, but it's definitely possible. McConnell, who covets his role as majority leader and spends the vast majority of his days ensuring he stays in that role, would face a dilemma he simply hasn't up to this point.

On the actual nominee

The actual selection does matter here. It may not seem like it, but Alexander made clear in his statement he wasn't an automatic yes. (That's not the case for everyone.) But to some degree the pressure on who, exactly, is selected may be minimized somewhat by the current realities.

The concern over Amy Coney Barrett had been that she'd be unpalatable to the GOP moderates -- specifically Collins and Murkowski -- due to her views on abortion. Well, Collins and Murkowski have already put their pre-election cards on the table. That doesn't mean Barrett is or will be the pick. That's the President's prerogative, though Republicans involved in the process told CNN she's viewed as the clear leader at the moment (and McConnell, while not putting his thumb on the scale, made clear to Trump in a phone call that the Republican conference is comfortable with Barrett, according to two people familiar with the matter). But it's an interesting element of all of this.

The politics

Let's start with the baseline that things are scrambled, and despite some early polling, nobody is exactly sure what this is going to mean for November.

But there are theories -- and watching how each side is lining up provides some insight, as does conversations with campaign operations on both sides.

Republicans

Aides, campaign strategists and members we've talked to over the weekend have warned that this vacancy, a vote before the election and the consequences or opportunities for a faster timeline are different for every single member running for reelection. For Gardner, a Republican in Colorado, who is facing a state that has changed dramatically in six years and is looking bluer, it's a tough vote. For Sen. Thom Tillis, a Republican from North Carolina, a southern state where a conservative base is far more motivated by the issue of abortion, less so. For Collins, who has already come out against moving forward before the election, this is an opportunity to assert an independent streak. The politics are all over the map here and McConnell is going to have to work through that with his members Tuesday when they meet for lunch.

Democrats

Democrats are furious and that furor is translating, at least in these early days, to the campaign trail. ActBlue, the Democratic small-dollar fundraising platform, reported more than $100 million in small dollar donations in a little more than 36 hours this weekend.

One thing is clear -- Democrats, from Joe Biden down, are moving quickly to put the focus on health care. It was a winning issue in 2018, before the pandemic it was going to be the central component of their campaigns, and with the Supreme Court set to take up a case that would strike down the Affordable Care Act, it will once again take center stage.

The Democratic options

It's important to remember. There are no options for Democrats to block this nomination if McConnell moves forward and has the votes. They can delay and make life more difficult and annoying for moving this nomination, but they can't block it. The only things they can do are 1) convince four Republicans that supporting a Trump nominee before the election is wrong or 2) retaliate in January if they win back the US Senate.

A little about the first

If you were watching Biden's message Sunday, it wasn't about what Democrats should do right now, but what he hopes Republican rank-and-file members will do. Biden's appeal is to convince Republicans on the fence that moving ahead with a nomination before the election or even if Trump losses is the wrong move.

And, the second

Senate Minority Leader Chuck Schumer told his caucus over the weekend that "if Leader McConnell and Senate Republicans move forward with this, then nothing is off the table for next year. Nothing is off the table."

Behind the scenes, Democrats are talking about a lot of steps they could take, including nuking the filibuster, if they win in November, even adding additional seats to the Supreme Court. But, right now, all of those things would depend on Schumer winning the Senate and having 51 votes. They are all hypothetical and future threats. And even if Democrats flip the Senate, you have to convince enough members of the caucus to vote to change the rules.

What to read

On the historic Senate fight to come, via Clare Foran, Manu Raju and Ted Barrett.

-On conservatives pressing for a quick vote, via Lauren.

-On Senate Democratic warnings of retaliation, via Manu.

-On the effect on the Arizona Senate race, via Ted, Manu and Alex Rogers.

-On who to watch for potential nominees, via Ariane De Vogue.

-Supreme Court prepares to start a new term with only eight, via Ariane.

-And this must read: 20 years of closed-door conversations with Ruth Bader Ginsburg, via Joan Biskupic.