President Donald Trump travels to Georgia on Monday in a bid to keep the U.S. Senate in the hands of his Republican Party, after his efforts to overturn his own defeat in the state have injected new uncertainty into a pair of races that are seen as too close to call.

President-elect Joe Biden also will travel to Georgia for a last-minute rally ahead of the Tuesday runoff elections, which pit a pair of incumbent Republican senators against two Democratic challengers.

If Republicans Kelly Loeffler and David Perdue successfully defend their seats, their party would maintain a 52-seat majority in the 100-seat Senate, giving them the power to block much of Biden’s agenda when he takes office on Jan. 20.

A sweep by Democrats Raphael Warnock and Jon Ossoff would hand control to Biden’s party, as Vice President-elect Kamala Harris would hold the tiebreaking vote in the 50-50 chamber. That would make it easier for Biden to enact further coronavirus relief and tackle climate change, as Democrats also control the House of Representatives.

None of the candidates won a majority in their November races, which spurred the runoff elections.

Biden narrowly won Georgia in November, breaking years of Republican dominance in the state. Trump has refused to acknowledge his defeat and his campaign has unsuccessfully sought to overturn the results in Georgia and several other battleground states.

Trump pressured Georgia’s top election official, Secretary of State Brad Raffensperger, on Saturday to “find” enough votes to overturn his defeat.

“There’s nothing wrong with saying, you know, that you’ve recalculated,” Trump said, according to an audio recording of the call released by the Washington Post. Raffensperger refused his request.

Democrats and election experts say Trump’s efforts almost certainly broke the law.

It is not clear whether Trump’s actions and his repeated claims of election fraud will affect the outcome of the Senate races. Strategists from both parties say the outcome could likely hinge on how many Republican voters participate on Tuesday, given strong Democratic early-voting turnout.

“If we get our vote out on Election Day then I think Perdue and Loeffler both have a very strong chance of winning,” Cobb County Republican Party Chairman Jason Shepherd told Reuters.

Trump warned Raffensperger on Saturday that Republican voters might be disheartened if Biden’s victory is allowed to stand.

“Because of what you’ve done to the president a lot of people aren’t going to vote, and a lot of people are going to vote negative,” he said on the call. He has previously called for both Raffensperger and Georgia Governor Brian Kemp, both Republicans, to resign for not backing his unsupported allegations of election fraud.

The campaigns have obliterated spending records and spurred unprecedented turnout. More than 3 million Georgians have already cast their votes and political groups have flooded the southern state with a tsunami of advertising.

Trump is due to visit Dalton, a city in the state’s heavily Republican northwest.

Biden will rally along with Ossoff and Warnock in Atlanta.