Mitch McConnell just conceded he might not have the Republican votes to block witnesses from testifying in Trump's impeachment trial

• Senate Majority Leader Mitch McConnell reportedly told his caucus on Tuesday that they haven't secured the votes necessary to block Democrats from calling witnesses to testify in the impeachment trial.
• McConnell reportedly compiled a list of "yes," "no," and "maybe" votes, but didn't show the whip count to his fellow senators.
• But Republican leadership is reportedly confident it can win over the necessary GOP votes by Friday. The party is arguing that calling witnesses would extend the trial indefinitely.
• Pressure on Republicans has intensified after The New York Times reported on Sunday that former national security adviser John Bolton wrote in his forthcoming book that the president told him last year he would withhold military aid to Ukraine until the country investigated his political rivals.
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Senate Majority Leader Mitch McConnell reportedly told his caucus on Tuesday that they haven't secured the votes necessary to block Democrats from calling witnesses to testify in President Donald Trump's impeachment trial.

McConnell told his fellow Republicans during a meeting on Tuesday afternoon that he doesn't currently have enough Republican votes to quash the Democrat-led effort, a vote for which is planned for Friday, The Wall Street Journal and other outlets reported.

McConnell reportedly compiled a list of "yes," "no," and "maybe" votes, but didn't show the whip count to his fellow senators.

But Republican leadership is reportedly confident it can win over the necessary GOP votes by Friday. The party is arguing that calling witnesses would extend the trial indefinitely.

Senate Democrats want at least four key witnesses, including former national security adviser John Bolton and acting White House chief of staff Mick Mulvaney, to testify. The vast majority of Republicans oppose calling witnesses, but a handful of GOP senators have expressed willingness to buck their party on the issue.

Pressure on Republicans has intensified after The New York Times reported on Sunday that Bolton wrote in his forthcoming book that the president told him last year he would withhold military aid to Ukraine until the Ukrainian president acceded to his demands for investigations into his political rivals.

Bolton's allegations contradict Trump's repeated claim that he didn't leverage the military aid to pressure Ukraine to investigate former Vice President Joe Biden and other Democratic opponents.

Trump's former chief of staff, John Kelly, said on Monday that he believes Bolton's allegations rather than Trump's denials. Kelly was among Trump's closest advisers for 18 months following a stint as secretary of homeland security.

But it remains unclear whether Democrats can gather the four GOP votes necessary to reach the 51-vote threshold to call witnesses.