Sabato’s Crystal Ball at the University of Virginia made the ratings change on Thursday morning. The forecaster pointed to tightening polls, an influx of money into the races and the possibility of runoff races as reasons for the change. Overall, Sabato’s Crystal Ball’s outlook for the Senate shows 50 seats leaning to Democrats, 47 leaning to Republicans and three toss-ups.

In response to the rating shift, GOP Senator David Perdue’s campaign said it knew “from day one” that this would be one of the closest races in the country and criticized Democrats for spending millions of dollars to aid opponent Jon Ossoff.

“They’ve resorted to lies about Senator Perdue to distract voters from Ossoff’s radical socialist agenda,” said John Burke, Perdue’s communications director. “The people of Georgia know Senator Perdue has worked hard to secure COVID-19 relief, support our military communities and restart our economy. They will re-elect him on November 3rd.”

The Ossoff campaign did not respond to Newsweek’s request for comment in time for publication.

During a televised debate Wednesday, the Democrat criticized Perdue’s record on health care and the coronavirus pandemic, in remarks that went viral. Ossoff called Perdue a “crook” and said the senator “in the middle of this health crisis is still supporting efforts to repeal protections for Georgians with preexisting conditions.”

According to the latest polls, the race between Ossoff and Perdue is neck and neck. The latest survey from Monmouth University, released Wednesday, found the two candidates in a statistical tie.

Georgia’s other Senate race is a special election that has more than 20 candidates on the ballot. But it’s mostly a three-way contest between Republicans Kelly Loeffler and Doug Collins and Democrat Raphael Warnock. Polls have shown Warnock in the lead, with Senator Loeffler and Representative Collins evenly splitting the Republican vote.

The Warnock campaign, in response to the race being moved to toss-up territory, said the church pastor is “finishing this campaign how he started and how he’s done throughout in his career—fighting for workers, families and Georgians.”

“We’re humbled that folks are picking up on the energy we’ve seen traveling across the state. Georgia is the battleground, and Reverend Warnock is the senator we need to protect access to affordable health care, voting rights and the things Georgians care about,” said campaign spokesman Terrence Clark.

Newsweek reached out to the Loeffler and Collins campaigns for comment on the ratings change from Sabato’s Crystal Ball but did not receive responses in time for publication.

The two highly competitive Senate races—especially the special election—could result in a runoff, which would put majority control of the chamber in limbo until after the new year.

If no candidate gets more than 50 percent of the vote on Election Day, Georgia law dictates that the top two finishers (regardless of party affiliation) compete in a runoff. The runoff would be held January 5, 2021.

The two Democratic candidates, Warnock and Ossoff, have been endorsed by Joe Biden and former President Barack Obama. In his endorsements, Biden praised both candidates for their focus on health care, voting rights and workers’ rights.

On the Republican side, Loeffler and Collins have been competing for President Donald Trump’s support. Trump has not endorsed anyone in the race, but during a campaign event in Atlanta last month, he said, “They’re going to be in there fighting, fighting, fighting…. And the only thing I know for sure, they’re all going to vote for me.”

Trump endorsed Perdue back in June, writing on Twitter: We need our Great David Perdue (@PerdueSenate) in the Senate to Drain the Swamp & Make America Great Again! His Radical Liberal opponent, Jon Ossoff (who we beat in 2017), supports LAWLESS Sanctuary Cities, wants to raise your taxes, & weaken our Great Military. He is a puppet."

The Senate races’ shift from leaning Republican to a toss-up mirrors what is happening in Georgia at the presidential level. According to polling from Monmouth University, the Biden campaign has picked up significant steam in the traditionally red state. The latest survey found the former vice president with support from 50 percent of registered voters, compared with Trump’s 45 percent.