WASHINGTON (AP) — Senate Majority Leader Mitch McConnell said Tuesday there's "no reason for alarm" as President Donald Trump, backed by Republicans in Congress, mounts unfounded legal challenges to President-elect Joe Biden's election victory — a process that could now push into December.

Republicans signaled they are willing to let Trump spin out his election lawsuits and unsubstantiated claims of voter fraud for the next several weeks, until the states certify the elections by early December and the Electoral College meets Dec. 14.

McConnell's comments show how hard Republicans are trying to portray Trump's refusal to accept the election results as an ordinary part of the process, even as it's nothing short of extraordinary. There is no widespread evidence of election fraud; state officials say the elections ran smoothly. The delay has the potential to upend civic norms, impede Biden's transition to the White House and sow doubt in the nation's civic and election systems.

Trump remained out of sight at the White House, tweeting his views, but the social media company Twitter swiftly flagged the president's tweets that he actually won the election as disputed.

"It's not unusual, should not be alarming," McConnell told reporters on Capitol Hill. "At some point here we'll find out, finally, who was certified in each of these states, and the Electoral College will determine the winner. ... No reason for alarm."

Democrats were livid, saying McConnell and Republicans in Congress are so afraid of Trump they are willing to risk the nation's tradition of an orderly transition.

Senate Democratic leader Chuck Schumer said the president is "undermining faith in our elections."

Biden, taking questions from reporters in Delaware, called the president's refusal to concede an "embarrassment."

"How can I say this tactfully?" Biden said. "I think it will not help the president's legacy."

Biden said he understands Trump voters' "sense of loss." But he said, "They understand we have to come together. ... We can pull the country out of this bitter politics."

Trump's GOP allies in Congress have largely declined to congratulate Biden, backing up Trump's efforts to pursue legal challenges, even though privately many Republicans doubt he has any legitimate path to change the outcome.

Republicans are increasingly pointing to a December deadline to allow Trump space to exhaust his legal challenges. That's when the states face a deadline to certify results and a Dec. 14 deadline for the Electoral College to cast its votes. It's also about the time it took to resolve the 2000 election dispute between Republican George W. Bush and Democrat Al Gore.

Yet, unlike the Bush-Gore election, which was held up over hundreds of contested ballots in one state, Florida, Trump's team is challenging the outcome in several states with tens of thousands of ballots. Trump would need to produce ample evidence of impropriety to undo Biden's lead, which appears unlikely.

Later, after a closed-door lunch with Vice President Mike Pence and Senate Republicans, McConnell insisted, "I don't think we're going to have an uninterrupted transition."

Democrats, meanwhile, are pushing ahead in preparation for the Biden administration, particularly the president-elect's immediate rollout of a sweeping COVID-19 plan.

On Tuesday, Schumer invited Biden adviser Vivek Murthy, the former surgeon general, to a private briefing with senators to discuss Biden's plan to tackle the coronavirus pandemic.

Democratic senators said it was like a cloud lifting as they heard plans for a comprehensive approach for bringing the COVID-19 crisis under control.

"Congress should pursue a strong, comprehensive COVID relief bill," Schumer said. He warned McConnell and Republicans not to block or settle for a more modest effort. "We cannot pretend this pandemic is nearly over," he said.

Trump and his GOP allies haven't offered evidence of election fraud, and their legal challenges have largely been rejected by the courts.

Still, Republicans are unwilling to stray from Trump, even in defeat, afraid of angering his most ardent supporters ahead of the Jan. 5 runoff elections in Georgia that will determine majority control of the Senate. Two Republican senators are struggling to keep their seats against Democratic challengers.

McConnell noted the potential turmoil during the transition in praising ousted Defense Secretary Mark Esper, whom Trump fired on Monday.

McConnell said he expects to speak "soon" with new acting Defense Secretary Chris Miller about threats from terrorists or foreign adversaries "who may seek to exploit a period of uncertainty."

He said the times call for "continued sober and steady leadership" at the Pentagon.

Both McConnell and Schumer were reelected as party leaders during private Senate elections Tuesday, but it's unclear whether McConnell will retain his role as majority leader or cede it to Schumer as the final races for the U.S. Senate play out.

Last week's elections left the chamber split, 48-48, heading into the new Congress next year. Republicans brushed back Democratic challengers in several states, but failed to lock down the seats needed to retain their majority.

The races for the two seats in Georgia heading to a Jan. 5 runoff are swiftly becoming a showdown over control of the chamber. The state is closely divided, with Democrats making gains on Republicans, fueled by a surge of new voters. But no Democrat has been elected senator in some 20 years.

Two other seats remain too early to call. In North Carolina, Sen. Thom Tillis is trying to fend off Democratic challenger Cal Cunningham in a tight race. Cunningham conceded on Tuesday, but The Associated Press has not yet called the race. Alaska GOP Sen. Dan Sullivan is favored for another term against Al Gross, an independent running as a Democrat.

Even if Republicans secure those final two races where ballots are still being counted, they would still fall short of the 51 seats needed.

The math has become more challenging for McConnell because the vice president of the party holding the White House casts the tie-breaking vote in the Senate. Next year that would be Vice President-elect Kamala Harris. That means 50 seats for Democrats would result in chamber control. But Republicans would need 51 seats to retain power.

The stakes are high for all sides, with strategists expecting an eye-popping $500 million could be spent in the weeks ahead.