The election will not only decide who will occupy the White House for the next four years, but also which party controls both the U.S. House of Representatives and the U.S. Senate.

All 435 seats in the House of Representatives and 34 seats in the Senate are up for grabs.

Republicans currently control the House while Democrats retain a narrow majority in the Senate.

See how the balance of power is playing out as election results come in:

Significant shifts and what to watch in the Senate race

Jim Justice is projected to win the Senate seat in West Virginia, which flips the state from Democrat to Republican. Incumbent Joe Manchin decided not to run for reelection, putting Justice against Democrat Glenn Elliot and Libertarian Party candidate David Moran.

ABC News also projects that former President Donald Trump will win in West Virginia. As Dan Hopkins, a professor of political science at the University of Pennsylvania, wrote for ABC News' live election coverage, "In most years, a Senate where every state votes for the same party for Senate and president is a Senate where the Democrats fall short of a majority."

Another Democratic seat was lost in Ohio, where Republican nominee Bernie Moreno is projected to take the Senate position previously held -- for three terms -- by Sherrod Brown, the Democratic incumbent. The presumed victory makes a large Republican majority in the Senate seem all the more likely.

In Maryland, Democratic Prince George’s County Executive Angela Alsobrooks is projected to win against former Gov. Larry Hogan, a moderate Republican. She is expected to replace Sen. Ben Cardin, also a Democrat, who did not run for reelection, putting the state's Democratic Senate seat at risk in a year where the party had none to lose if they hoped to retain their narrow majority.

Alsobrooks currently serves as the first woman elected to a county executive position in Maryland, and she now seems positioned to become the state's first Black senator. She would also be making history, as Alsobrooks and Lisa Blunt Rochester are projected to be the first two Black women to serve on the Senate at the same time.