CNN  — 

Two closely watched runoff elections in Georgia on Tuesday will determine which party controls the US Senate.

Democrats Jon Ossoff and the Rev. Raphael Warnock are looking to defeat incumbent Republican Sens. David Perdue and Kelly Loeffler, respectively.

The races will determine whether Republicans keep control of the Senate, which will greatly affect the kind of legislation President-elect Joe Biden would be able to pass through the chamber once he takes office later this month.

The Senate would be tied 50-50 Republicans and Democrats if Ossoff and Warnock both win their races, but Vice President-elect Kamala Harris would be able to act as a tie-breaking vote, which would give control of the chamber to Democrats. If Republicans win either or both of the seats, the GOP will keep control of the chamber.

Biden, who won Georgia in the presidential election, and President Donald Trump both traveled to the state on Monday to campaign for their party’s candidates.

Here’s what you need to know about how to watch CNN’s election coverage.

Why are there runoff elections?

Under state law, Senate races advance to a runoff if no candidate surpasses 50% of the vote, as was the case for both of Georgia’s US Senate seats after the November election. Perdue received 49.73% of the vote and Ossoff received 47.95%, and Warnock received 32.9% compared with Loeffler’s 25.91% in the special election.

What time does CNN’s coverage start?

CNN’s coverage of the runoff elections starts at 4 p.m. ET on Tuesday. Tune in to CNN or CNN International, or watch on mobile devices via CNN’s apps for iOS and Android, and via CNNgo apps for Apple TV, Roku, Amazon Fire, Chromecast and Android TV. You can also follow CNN’s live election coverage on CNN.com.

Who are the candidates?

Kelly Loeffler

In December 2019, Loeffler was appointed by Republican Gov. Brian Kemp to take over the Senate seat previously held by Republican Johnny Isakson, who retired over health concerns. Loeffler, who was sworn in to office in January 2020, was a political novice, a prominent GOP donor and a businesswoman.

She was an executive at a financial services firm in Atlanta but left the post to serve in the Senate. She is also known as a co-owner of the WNBA’s Atlanta Dream. She had considered running for the Senate in 2014.

Loeffler is facing off against Warnock.

Raphael Warnock

Warnock, a Democrat, is a senior pastor at Atlanta’s historic Ebenezer Baptist Church, which has long been a haven for the Black freedom struggle. Dr. Martin Luther King Jr. became a co-pastor of Ebenezer Baptist Church with his father in 1960.

In a video announcing his candidacy last year, Warnock described his path from Savannah’s Kayton Homes housing project to the pulpit.

“Some might ask why a pastor thinks he should serve in the Senate,” said Warnock. “I’ve always thought that my impact doesn’t stop at the church door. That’s actually where it starts.”

Jon Ossoff

Ossoff, a Democrat, rose to national prominence during a 2017 special House election that the political newcomer nearly won in a longtime conservative stronghold in Georgia. He ultimately lost to Republican Karen Handel in what was at the time the most expensive House race in history.

Ossoff describes himself as a media executive, investigative journalist and small business owner on his campaign website. He began working with a former BBC journalist, Ron McCullagh, in 2013, and then used money from an inheritance to buy a stake in McCullagh’s investigative film company and renamed it Insight TWI, according to The Atlanta Journal-Constitution. The company has produced documentaries on mass killings and sexual slavery by ISIS, and a corruption investigation on judges in Ghana.

Ossoff is attempting to unseat Perdue.

David Perdue

Perdue, a close Trump ally, has served as a senator from Georgia since his election in 2014.

Perdue has served on the Armed Services, Banking, Budget, and Foreign Relations committees, according to his Senate website.

He had never run for public office before 2014, according to his Senate website, and prior to running for office was the CEO of Reebok athletic brand and Dollar General stores.

Perdue’s term technically expired Sunday when a new Congress was sworn in, leaving his seat temporarily vacant, according to Sydney Butler, chief of staff to the secretary of the Senate – who oversees the chamber’s operations and procedures. Officials in Georgia Gov. Brian Kemp’s and Perdue’s offices say that even if he is projected the winner Tuesday, the seat will remain vacant until the runoff results are certified – which could take up to two weeks.

CNN’s Madison Park, Eric Bradner, Clare Foran, Donald Judd, Alex Rogers and Ryan Nobles contributed to this report.