WASHINGTON — Congressional races across the country will decide the balance of power in both the U.S. Senate and the House of Representatives.

Republicans are predicting a massive red wave amid concerns about the economy, crime and President Joe Biden’s leadership. But Democrats are hoping that a backlash against the Supreme Court’s reversal of Roe v. Wade will save them.

The party that occupies the White House has suffered significant losses in nearly every president’s first midterm election for more than a century.

Republicans need one additional Senate seat to gain control of that chamber, which could happen if Democrats lose in Nevada, Arizona or Georgia. But Republicans will also need to hold onto seats in Pennsylvania, Ohio and Wisconsin.

In the House, Republicans are widely expected to win back power after four years in the minority. The GOP’s estimated gains vary widely though, from a handful of seats to 25 or more.

But election officials say voters may not find out who the winner is in key races on Tuesday night or which party will win control of Congress — noting the delay is normal and necessary to ensure all votes are carefully counted.

Some races could drag on for days, or even weeks, because some are already being contested in court. Additionally, in Georgia, if one candidate doesn’t get at least 50% of the vote, that will head to a runoff.

Track the balance of power in both the Senate and House in the interactive graphic below as results roll in.

Nexstar’s Washington DC Bureau and the Associated Press contributed to this report.