The surge in new voter registration and the historic jump in nation-wide early voting provide concrete testimony of the deep political passions stirred by this year’s midterm elections.

This enthusiasm — paradoxically — complicates the already vexing question of which parties will control the House of Representatives (the trends appear to favor the Democrats) and the U.S. Senate, where the Republicans have an edge. Across the nation, 36 governorships are on the block and Democrats are expected to make gains, but Republicans are forecast to have an upper hand. At least nine of the contests, however, are too close to call.

After the agonizing reappraisals triggered by Donald Trump’s presidential victory, pollsters and analysts have been cautious. The influx of new and early voters is keeping the pollsters on their toes. Election projections use algorithmically massaged historic behavior to forecast probable results.

Nate Silver, the proprietor of FiveThirtyEight, warns that data for off-year elections is less reliable than presidential years. FiveThirtyEight and other major news outlets, such as Politico and the Upshot of the New York Times, adjust accordingly. In the end, all elections are about turnout, and this year, how many voters turn up to vote for which parties will have historic significance. Also of import will be how many citizens will be barred from voting. Witness Georgia, where charges of voter suppression are rife.

Although Democrats have much to win, Republicans, with their monopoly on all three branches of national government, have the most to lose.

It's All About Trump

Two headlines suggest the different points of view within the GOP.

“Trump has hijacked the election: House Republicans in panic mode,” Politico proclaims, adding: “Worries deepen that Trump’s charged immigration rhetoric will cost the GOP more seats.”

Meanwhile, Daniel McCarthy, a leading intellectual voice on the right, in a New York Times op-ed essay writes: “Few Republicans running this year seem to understand what gave Mr. Trump his edge in 2016 — it was not that he was simply combative and rhetorically right wing. It was that he had a vision of what it meant to make America great again, by making the Republicans a party for the nation again.”

However the results break, and it may be 36 to 48 hours before a final picture comes into focus, the 2018 midterm elections will determine the contours of Trump 2.0. And Trump 2.0, in turn, will establish the foundation of the 2020 presidential race. Here’s what to keep an eye on.

The House Of Representatives

The Real Clear Politics average of polling data, a generally cautious measure, gives Democrats a 7.3 percent edge to take over the House.

FiveThirtyEight, which was less wrong two years ago than any other major media outlet, projects that Democrats have an 87.4 percent chance of reaching the 218 seats needed to elect a Speaker. That’s seven out of eight chances.

The site also gives the Democrats an 80 percent chance of gaining up to 59 seats. They currently hold 194 out of the 435.

The Republicans, according to the FiveThirtyEight model, have a one in eight chance, or 12.6 percent likelihood of remaining in power.

A worst-case scenario does exist for the Democrats, and FiveThirtyEight concluded that there is a 10 percent chance the party could gain less than 21 seats. (They need a 24-seat gain to assume power.)

Such an outcome would be as significant an upset as Trump’s surprise election two years ago. Probably even more electrifying. But it is possible. So thin are the margins separating candidates in so many districts that a handful of votes multiplied by a handful of districts could have national consequences.

Still, the non-partisan Cook Political Report says Republicans and Democrats are essentially tied in 30 districts. But as an indication of how fluid the House races are, Cook on Monday shifted it classification of nine previous undecided seats to the Democrats, reinforcing the conventional wisdom that trends favor the Democrats.

The U.S. Senate

Real Clear Politics gives the Republican an edge in the Senate. With 51 seats required for a majority, RCP concatenates 50 for the GOP, 43 for the Democrats, with seven still up in the air.

FiveThirtyEight is in line with the thrust of this trend. It’s projection, however, is more of a mirror opposite of how it sees the House: a five in six chance (83.6 percent) that the Republicans will keep control of the Senate, and a one in six chance (16.4 percent) that the Democrats can stage an upset.

And, here are the races you will want to keep an eye on. In Texas, perhaps the nation's highest profile Senate race, Democratic Rep. Beto O'Rourke is looking to unseat Republican Sen. Ted Cruz, who has had the president campaigning for him. In North Dakota, Missouri and Florida, three Democratic incumbents — Heidi Heitkamp, Claire McCaskill and Bill Nelson — are trying to hang onto their seats in states won by President Donald Trump. In Nevada, Republican Sen. Dean Heller is fending off a challenge from Rep. Jacky Rosen in a state that Hillary Clinton won by a little more than two percentage points. Nevada will be a key race for the Democrats as some believe that if they can't win there, they have little hope of taking the Senate.