Updated

Sen. Jeanne Shaheen, D-N.H., said that some Republican lawmakers who are refusing to accept Joe Biden as president-elect "are bordering on sedition and treason."

"These senators and members of Congress who have refused to acknowledge that we had a free and fair election in which Joe Biden beat Donald Trump by over 7 million votes, are bordering on sedition and treason," Shaheen told CNN’s Jim Sciutto. 

Although a growing number of Republicans have acknowledged Biden’s win after the electoral college voted for him on Monday, President Trump has urged Sen. Majority Leader Mitch McConnell to "get tougher" in the election fight. 

In a series of Twitter attacks Friday morning against other fellow Republicans, Trump also targeted Georgia Gov. Brian Kemp and Rep. Liz Cheney of Wyoming.

"[McConnell] and Republican Senators have to get tougher, or you won’t have a Republican Party anymore. We won the Presidential Election, by a lot. FIGHT FOR IT. Don’t let them take it away!" Trump charged on Twitter.

McConnell, the longtime GOP senator from Kentucky who has led the Senate for the past six years, recognized Biden’s victory in a Tuesday speech on the floor of the Senate, noting "the electoral college has spoken." 

"So today, I want to congratulate President-elect Joe Biden," McConnell said. "The president-elect is no stranger to the Senate. He has devoted himself to public service for many years."

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McConnell also asked his Republican colleagues in the Senate not to try and contest the election results on Jan. 6, when a joint session of Congress formally accepts the Electoral College count. While some strong Trump allies in the House plan to call for a debate, McConnell’s move could effectively end any hopes of a last-minute reprieve for the president. A majority of both houses of Congress would be needed to upend the election results.

Fox News' Paul Steinhauser contributed to this report.