Voters across the country are heading to the polls as former President Donald Trump and Vice President Kamala Harris remain locked in a dead heat.

The race is particularly tight in Pennsylvania, which holds 19 electoral votes and could be a deciding factor in which candidate reaches the 270 electoral votes needed to win.

Trump and Harris both spent time campaigning in the state on Monday (November 4). Trump started his day in North Carolina before heading to Pennsylvania for a pair of rallies. He then wrapped up his campaign with a speech in Michigan, just as he did in the previous two presidential elections.

Harris spent her entire day in Pennsylvania, making her final push to voters with rallies in Philadelphia and Pittsburgh, followed by a concert in Allentown.

In addition to deciding who will be president, voters will also determine which party controls the House and Senate. All 435 seats in the House of Representatives and 34 seats in the Senate are up for grabs. Currently, Republicans control the House, while Democrats hold a narrow majority in the Senate.

Polling website 538 gives Republicans a 90% chance of regaining control of the Senate and a 52% chance of maintaining their House majority.

In the Senate, Democrats face a tough map as several incumbents are up for reelection in reliably red states. Republicans only need to pick up two seats to flip the chamber.

One of the key Senate races to watch is in Montana, where Democratic Senator Jon Tester is running against businessman and former Navy SEAL Tim Sheehy. Tester is currently trailing in the polls, and a loss here could likely hand Republicans the Senate majority.

In Ohio, Democratic Senator Sherrod Brown is running for his fourth term in a state that has gone from purple to red, imperiling his chances of reelection. He is facing Bernie Moreno, a Colombian immigrant and businessman. Moreno has significantly cut into Brown's edge in the polls, making this race one to watch.

In Michigan, the retirement of Democratic Senator Debbie Stabenow has opened a top opportunity for Republicans. The race pits former GOP Rep. Mike Rogers against Democratic Rep. Elissa Slotkin, who currently holds a slight edge in the polls.

In Pennsylvania, Democratic Senator Bob Casey is facing a well-heeled opponent in Dave McCormick, a former hedge fund executive. Casey currently holds a narrow lead in the polls, but this race is expected to be fiercely competitive.

Finally, in Arizona, the retirement of independent Senator Kyrsten Sinema, who caucuses with Democrats, has set up a prime flip opportunity for Republicans.

In the House, Democrats would need to wrest four seats from Republicans to regain majority control.

The results of these key races will determine the balance of power in Congress for the next two years.

While results will start coming in after 7 p.m. ET, the race between Harris and Trump may not be decided on election night as many states work to count the large number of early votes that were cast.

Georgia will be the first swing state to wrap up voting, where the polls will close at 7:00 p.m. ET. Next up, the polls in Ohio and North Carolina will close thirty minutes later, at 7:30 p.m. ET.

Pennsylvania polls will close at 8:00 p.m. ET, as will polls in parts of Michigan. By 9 p.m. ET, all the polling locations in Michigan will be closed, as will the polls in Arizona and Wisconsin. Polls in Nevada will close at 10 p.m. ET.

Before you head out to vote, you can check your polling location here.

iHeartRadio will have full coverage of the election on 24/7 News Radio.

Armstrong & Getty