Analysis by Stephen Collinson, CNN

(CNN) -- The House of Representatives is still too close to call after an acrimonious midterm election as Democrats seek to win a key check on President Donald Trump's White House. And so far, Republicans are performing strongly in several Senate races though key races remain on a knife edge, reflecting the deep political divide right down the middle of America.

Democrats have won the first two of the 23 seats they need to seize back the House for the first time in eight years. But Republicans look well positioned to keep the Senate after Marsha Blackburn won one of the key contests in Tennessee, according to a CNN projection.

But other high-profile contests have yet to be decided.

Florida is living up to its history as a cliffhanger state, with Democratic Sen. Bill Nelson hoping late votes in Democratic counties could narrow his slim deficit to his challenger, the outgoing Gov. Rick Scott. Democratic gubernatorial candidate Andrew Gillum is narrowly trailing his challenger Rep. Ron DeSantis.

In Texas, Democrat Beto O'Rourke and incumbent Sen. Ted Cruz are neck-and-neck as votes are counted in Texas and the race remains too early to call.

But incumbent Democrat Sen. Joe Donnelly is trailing his Republican challenger in Indiana with more than half the votes counted. The Democrats need to pick up two Senate seats and not lose any to have a majority.

Trump is trying to defy historic omens that suggest that commanders in chief often get a rebuke from voters in the midterm election of their first term. His approval rating -- 39% in the latest CNN poll -- is within the range where the President's party typically suffers heavy losses on Capitol Hill.

But Trump is such an unusual politician who has made a career overturning conventions and expectations that it's possible he will defy ominous precedents. His connection with his most loyal fans remains so intense that some pundits believe he could help the GOP pull off a surprise.

Preliminary exit poll data found that Trump was a factor for almost two-thirds of House voters. About a quarter supported him and almost 40% said their vote was in opposition to the President. Two-thirds of voters said that they decided how to vote before the last month of the election. Only 1-in-5 decided in the last month and even fewer said they made up their mind in the last few days or the last week.

Change in the air?

If Democrats do manage to take the House, they will be in position to provide the first institutional check on Trump's presidency -- a role Republicans have chosen not to play given his political dominance on the right.

A loss of the House will also trigger significant second guessing of the President's tactics, given that he chose not to make the booming economy his primary midterm argument, instead turning to a searing indictment of Democrats focusing on immigration and laden with racial language.

Trump is still trusting his feel for what voters want to hear. But if Democrats have a good night, the entire premise of his presidency -- an incessant effort to please his loyal political base, will be called into question. But if Republicans do better than expected, Trump will be able to claim vindication for his campaign strategy and his unconventional approach to the presidency.

"There's a great electricity in the air, like we haven't seen, in my opinion, since the '16 election. So, something is happening," Trump told reporters on Monday, shrugging off suggestions that Democrats had the momentum.

It would take a disastrous showing for Republicans to lose control of the Senate since most of the endangered lawmakers up for re-election are Democrats from conservative states like Indiana, West Virginia, Montana and North Dakota, where Trump won big two years ago and is still wildly popular.

For Democrats to have any chance, they need to win at least one of the races in Arizona, Texas or Tennessee, which have not traditionally been favorable to them in recent decades and then virtually run the table in other toss up states.

Waiting for results

The President planned to have dinner with his family and to watch the results, which could have a profound impact on the rest of his term and could reshape Washington's balance of power, in the residence of the White House.

He was due to be joined by Republican megadonor Sheldon Adelson, Blackstone CEO Stephen Schwarzman and the President's ex-campaign aides, David Bossie and Corey Lewandowski, a source familiar with the guest list said.

Two other sources close to the White House said that Trump is already blaming retiring House Speaker Paul Ryan for what the President's team is billing as a bad night.

"He is really angry at Ryan," one source said on "everything."

Alongside all 435 House seats and a third of the Senate on the ballot on Tuesday are 36 gubernatorial races. Several have history making potential, especially in Florida where Tallahassee Mayor Andrew Gillum, a Democrat, is trying to become the state's first African-American governor in an ill-tempered duel with former Rep. Ron DeSantis, a Trump favorite. In an even more bitter contest that has been rocked by race rows and feuds over ballot access, Democrat Stacey Abrams is trying to become the nation's first black female governor in Georgia.

A CNN/SSRS poll released Monday showed Democrats with a gaping 55% to 42% lead over Republicans among likely voters in a generic congressional ballot. Trump was badly underwater among women voters -- who favor Democrats 62% to 35% -- a gender gap, that if borne out by real votes, could prove devastating to Republican hopes.

In the latest forecast by CNN's Harry Enten, Democrats are tipped to win 226 seats and the House majority while Republicans will win just 209 seats. Republicans are expected to hold 52 Senate seats and to retain their majority.