• "Democrats are unified, Republicans are not and that's what gives them the advantage," GOP pollster Frank Luntz told CNBC on Tuesday morning.
• Luntz's remarks referred to Tuesday's Georgia Senate runoff elections and Wednesday's Electoral College confirmation vote.
• "I think the next 48 hours are going to be among the worst for the GOP," Luntz said.

GOP pollster and strategist Frank Luntz believes that Democrats hold the upper hand in Tuesday's Georgia Senate runoff elections, warning of disappointment for Republicans in those pivotal races and in Wednesday's upcoming Electoral College presidential confirmation vote on Capitol Hill.

"There is a greater divide in the Republican Party than there is in the Democratic Party," Luntz said in an interview on CNBC's "Squawk Box" on Tuesday from Georgia. "The party is in the process of tearing itself apart and you don't do that now, when you're this close to the most important Senate election, literally, in a lifetime. Democrats are unified, Republicans are not and that's what gives them the advantage."

"I think the next 48 hours are going to be among the worst for the GOP," he added.

In Georgia, Republican Sen. Kelly Loeffler and Republican David Perdue, whose Senate term just expired Sunday, are facing off in Tuesday's election against Democratic challengers Rev. Raphael Warnock and Jon Ossoff, respectively. Loeffler's term didn't expire because she was appointed.

If both Democrats win, they would secure a 50-50 split for their party in the Senate, making Vice President-elect Kamala Harris the tiebreaking vote. It would give Democrats control of both the Senate and the House of Representatives as well as the White House after President-elect Joe Biden's inauguration on Jan. 20. 

One day after the Georgia runoffs, Congress is set to convene Wednesday in a joint session to approve the Electoral College vote, which took place in December and gave Biden a 306-232 victory over President Donald Trump. However, Trump has refused to concede to Biden and has repeatedly and falsely claimed he would have actually won the presidential election had it not been for widespread voter fraud.

At a Georgia rally Monday evening for Loeffler and Perdue, Trump declared he would "fight like hell" to hold on to the presidency and appealed to Republican lawmakers to reverse his election loss to Biden. Loeffler, who joined Trump, told the crowd she'll join senators formally objecting to Biden's win. Perdue won't be eligible to vote.

Luntz contended that Trump's baseless claims of voter fraud, especially in Georgia, where the president has attacked elected Republicans, have been hurtful during the Senate runoff races. Trump repeated many of those discredited statements at Monday's rally.

"Democrats are voting in record numbers over the last two, three weeks. Republicans are being told to stay home and Donald Trump, when he shows up to deliver that final rallying cry, he spends as much time talking about his own election as he does about the Republicans," Luntz said.

The pollster said he believes Trump will remain entrenched in the political world after he leaves the White House, continuing to flex his electoral influence with his core supporters in a manner that could cause further fracturing among the Republican Party.

"I think Trump is not only going to stay involved, I think he's going to be active over the next couple years and that's going to be very difficult for the Republican Party because Trump is already calling on primary challenges to incumbent Republicans in the Senate, in the House and for governor," Luntz said. "That spells a lot of chaos within the GOP at a moment when the public is saying to both political parties, 'Just govern. Please, just govern.'"

— The Associated Press contributed to this report.