By Lauren Fox and Jeremy Herb, CNN

(CNN) -- House Republicans are in the political fight of their lives as they try to hold onto their majority. But while they hope for the best, some are preparing for the worst: a Democratic takeover where oversight of the Trump administration spans every committee and essentially halts the GOP's legislative agenda for the next two years.

While on the campaign trail, conservatives use the threat of a Nancy Pelosi-controlled House to fire up their base, but GOP congressional aides say detailed plans aren't yet being drafted in case of a Democratic wave. Instead, the focus remains on holding onto their majority — because, as veteran House Republicans know, the House minority has the least amount of power on Capitol Hill.

Still, some Republicans are looking back at what happened the last time the President's party lost control of the House — when the GOP was victorious in 2010 — to study how the Obama administration handled rigorous oversight by the other side.

Adding to the uncertainty is the fact that a slew of Republican committee chairmen are retiring, opening up top slots on the House Oversight and Judiciary committees, where some of the biggest political battles of the new Congress would unfold.

The jockeying has already begun for those spots, regardless of which party wins next month, and the outcome of those inside-Washington-baseball races will set the tone for showdowns over public hearings, requests for documents, subpoenas — and even how an impeachment process could play out. Whoever fills those roles in a Democrat-controlled House would become the face of the GOP resistance and the leading attack dog defending the Trump administration.

"If the investigations are going to be as heated as we anticipate them being, it would benefit Republicans to have a fighter in that position because it is just going to be constant bomb throwing, and you want people to be able to push back," one House Republican aide told CNN.

Another Republican aide said of the Oversight Committee: "We can't have a wallflower. ... It needs to be a bulldog."

A new reality

Republicans from either the House or the Senate don't want to talk about being in the minority mid-election. Some members who CNN contacted declined to talk or said that they aren't going to answer hypothetical questions about a reality they hope won't befall them.

Sen. John Kennedy, a Republican from Louisiana, said he'd "cross that bridge when we come to it."

"I'm not prepared to concede that," Kennedy said.

A shift to the minority would be uncharted territory for most. It's been nearly a decade since the party took control of the House, with many members never having experienced the minority in their congressional careers.

"It's a different mentality," Former Rep. Charlie Dent, a Republican from Pennsylvania, said. "I went from the majority to the minority. It is a bit of a humbling experience."

Along with not setting the floor agenda, members in the minority get fewer staff on the committees and are forced into a reactive position rather than one where they control the message with the gavel.

Tim Chapman, the president of Heritage Action, told CNN that he's instructed leadership to try to develop a legislative agenda to counter Democratic investigations on Capitol Hill and set up the party to win in 2020 if they lose the midterms.

"So many people right now are focused on trying to find a way to hold the House. ... People are too busy to go toward a plan B," Chapman told CNN. "If (Democrats) do take the House, we all know what is going to happen. We know exactly what people's different roles will be. Democrats are going to do the investigations, they are going to overreach, and Republicans are going to have to make the case that this is bad for the country."

Committee slots have big implications

Republicans have a host of vacancies atop their congressional committees next year, and the lawmakers they select to lead the panels will set the course for how Republicans fight back over the next two years if they're in the minority.

That's particularly true on the Judiciary Committee, which would be in charge of any impeachment proceedings, and the Oversight Committee, whose Democratic chairman would have a wide lane to investigate the President and his businesses.

The situation is fluid for Republicans in part because Ohio Rep. Jim Jordan, a co-founder of the conservative House Freedom Caucus, is mounting a bid for speaker.

Republican sources say if Jordan's bid is unsuccessful, he could try to leverage the support of Freedom Caucus lawmakers for a perch atop one of those committees, which would give Republicans an attack dog who relishes battling with Democrats.

At the same time, the Freedom Caucus has alienated some rank-and-file Republican members, who could balk at the idea of rewarding rebelliousness with a committee gavel.

A source close to Jordan said that the Ohio Republican is focused only on his bid for speaker, and is not thinking about the committee posts.

Jordan declined to discuss the committees next year, telling CNN last week that he was running for speaker. Freedom Caucus Chairman Mark Meadows also declined to discuss his or Jordan's prospects for the next Congress.

Several other Republicans who haven't been as vocal in the fights over Russia and the FBI are already openly running for the Republican committee slots.

Rep. Doug Collins of Georgia and Rep. Steve Chabot of Ohio are both pursuing the Judiciary Committee gavel, and Rep. Steve Russell of Oklahoma is seeking to lead the Oversight Committee. Conversations with members of the Republican Steering Committee, which selects committee leaders, are already underway.

Collins told CNN that he's focused on keeping the Republican majority. But if Democrats do take over, he hopes to look for ways to work together on legislation and reform — though he's expecting that Democrats will try to use the panel to go after Trump, and he would be ready to push back.

A careful balance

Republicans say that they learned a series of lessons from handling oversight into the Obama administration after the 2010 election that could be useful to Democrats if they take control in November.

The fireworks that usually consumed the Oversight Committee often grabbed headlines and animated the conservative base as they held the attorney general in contempt of Congress, investigated the IRS and convened a blockbuster hearing into the terrorist attack in Benghazi, Libya.

But in the minds of some members, Republicans also overreached at times — and they believe Democrats could easily make the same mistake.

One Republican member running for re-election who spoke on the condition of anonymity told CNN the fear is that the House would be "tied up in knots" with partisan fights over investigations just as the country prepares for a presidential election.

"If it is just investigations for the sake of investigations, then I think the best thing we can do is just let them do it and expose it," the Republican said. "If they are just investigating to tie up the President's agenda, then I think the best thing we can do is help the American people see what is really happening."

The key for Republicans will be to decide when to fight back and when to let Democratic oversight speak for itself. On the one hand, a midterm election where Republicans are forced back into the minority is a referendum on Trump, a fact that could make them less likely to want to stick their necks out for some of the Trump administration's more controversial actions that, up to this point, many Republicans have held back criticizing.

Republicans will also have to pick their moments to protect Trump, however. One Republican aide told CNN that some are beginning to study how the Obama administration handled oversight and subpoena requests from Congress, a potential guidepost for how Trump should respond.

Democrats have been careful to discuss their plans for investigations and subpoenas, fearful the party could count on a victory before they actually win. But, Pelosi, the House minority leader, told CNN's Dana Bash on Monday that she would potentially use subpoena power as a negotiating tool.

"Subpoena power is interesting, to use it or not to use it," Pelosi told Dana Bash at the daylong CITIZEN conference put on by CNN. "It's a great arrow to have in your quiver in terms of negotiating on other subjects."

Wrapping their own investigations, too

With Election Day nearing, Republicans are racing to complete their joint investigation into how the FBI and Justice Department handled the Hillary Clinton and Russia investigations.

The investigation is run by House Judiciary Chairman Bob Goodlatte and Oversight Chairman Trey Gowdy, who are both retiring at the end of the year. Even if Republicans keep control of the committees, Goodlatte and Gowdy are expected to issue a report or summary of their findings before the new Congress is seated, according to Republican sources.

Interviews have ramped up even with the House out of session — three witnesses testified last week and another three interviews are slated for this week — as Democrats have signaled that investigation would fizzle if they control the House.

"This whole line of questioning has been made-for-TV, and the sooner we can put an end to it the better," said Maryland Democratic Rep. Jamie Raskin.

Arguably the biggest committee fights to date over Russia and the Justice Department occurred in the House Intelligence Committee, where lawmakers remain bitterly divided over the outcome of the panel's probe into Russian election meddling.

Both Chairman Devin Nunes and ranking Democrat Adam Schiff are likely to stay atop the panel, even if their roles are reversed next year — and their fight over the Russia probe is unlikely to cease should Schiff re-open the investigation as he's signaled (House Republicans wrapped their Russia investigation in March).

"For two years we've been force feeding this Russia Kool-Aid to the American people," Nunes told Fox News last month. "Now this thing has just gone on so long that it is scary to see the mainstream media, many Americans who have brought into this Russia Kool-Aid. It's really, really scary."