Trump's first 2 years will be shaped by who wins the House. We may not know the outcome for days.

Donald Trump is now the president-elect , and Republicans have gained control of the US Senate.

But we still don't know who controls the House of Representatives, and the outcome will have major implications for the first two years of Trump's second term.

As of Wednesday morning, both Democrats and Republicans had a plausible path toward winning the 218 seats necessary to hold the majority, though Republicans were projecting confidence that they would pull it off.

"As more results come in it is clear that, as we have predicted all along, Republicans are poised to have unified government in the White House, Senate, and House," said House Speaker Mike Johnson in a statement on Wednesday morning. "We will continue to monitor the results and ensure every legal ballot is counted throughout this process."

Democrats have declared victory in three GOP-held seats in New York, and the party is projected to pick up an additional seat in Alabama. But Republicans picked up Democratic-held seats in Pennsylvania and Michigan, along with three seats in North Carolina.

In order to flip the chamber, Democrats would need to make a net gain of four seats.

The results in several other battleground districts have yet to be determined, and many of them are in California, which has historically taken days to count ballots.

A Democratic House would be a major constraint on Trump's power

Historically, newly elected presidents have typically enjoyed unified government at the beginning of their terms.

The last time that a president entered office without control of both chambers of Congress was in 1988, when President George H.W. Bush was elected alongside Democratic majorities in both the Senate and House.

But to get an idea of what it would look like for Trump to share power with a Democratic-led House, one only needs to look back to the 2018 midterm elections, when a Democratic takeover in the House drastically altered the course of Trump's first term.

The most significant impact was that Democrats had the power to investigate and impeach Trump, which they ultimately did twice: Once in 2019 over Trump's attempt to leverage military aid in order to get Ukraine to investigate then-Vice President Joe Biden, and again in early 2021 after the January 6 insurrection. Trump was acquitted by the Senate both times.

Furthermore, Trump was no longer able to pursue the kinds of party-line priorities of his first two years, including the Tax Cuts and Jobs Act of 2017 and an attempt to repeal the Affordable Care Act.

Aside from must-pass legislation like government funding and defense bills, the only major legislative accomplishments of that period included massive economic stimulus bills to address the effects of the COVID-19 pandemic in 2020.

Many of the provisions that tax bill are set to expire next year, including income tax cuts, an expanded child tax credit, a deduction for small businesses, and a rollback of the estate tax. Allowing those provisions to simply expire would cause most Americans to experience a major tax hike.

Republicans have promised to extend those tax cuts, but if Democrats control the House, the parties will have to work together to get it done — and Democrats will be able to make demands.