It is not at all clear that 51 Republican senators, much less any Democrats, would agree to call Biden, but there is no doubt he will be part of the argument.

One key figure in the Ukraine affair, however, appears to have faded from view, even as impeachment reaches a climax. The whistleblower who started the whole investigation remains anonymous. The details of the whistleblower’s actions by which the whistleblower brought the Ukraine matter to the attention of the intelligence community to House Democrats, and ultimately to the world, remain unclear.

Democrats, who once hoped to feature public testimony by the whistleblower, argue that the account is no longer needed given the other evidence which they say proves Trump pressured Ukrainian President Volodymyr Zelensky to investigate Hunter Biden and the 2016 election. The whistleblower would have nothing to add, Democrats say, and could suffer recriminations and possibly physical danger if the whistleblower’s identity were known.

On the other hand, is the Senate really going to try the president and take a vote on his removal on the basis of an investigation with such murky origins?