(CNN) The news, first reported by The New York Times Sunday night, that President Donald Trump had told national security adviser John Bolton directly to continue to withhold approved military aid to Ukraine until that country agreed to announce investigations into Democrats, and specifically former Vice President Joe Biden, is an absolute bombshell with the very real possibility of fundamentally altering the calculus for Republican senators in the ongoing impeachment trial.

The accusation is made in a draft manuscript of Bolton's time in the Trump White House and, for the first time, would provide -- if confirmed -- direct evidence that Trump not only personally ordered the hold but did so to target the leading Democratic candidate against him in 2020. Bolton's claim -- again, if confirmed -- would be a smoking gun for Trump's use of his office for personal and political gain. Period.

Which brings us to the debate within the Senate over whether any witnesses will be allowed to testify in the trial of Trump and, if so, who.

Prior to the Bolton news on Sunday, GOP sentiment seemed to be leaning away from allowing witnesses, with Alaska Sen. Lisa Murkowski, a key swing vote, offering criticism of the manner and style used by the House Democratic impeachment managers to make their case.

While official Washington is still processing the Bolton news, it's hard to see both the accusation and the initial reaction to it not altering that voting calculus for Republicans.

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