Has the Trump impeachment drama reached its Brett Kavanaugh or Clarence Thomas moment? That would be the moment when, after the hearings are more or less done and it looks like the target will survive, the Democrats confect a last ditch scandal to block, in the case of the two justices, Senate confirmation or, in the case of President Trump, acquittal.

We confess we’ve been expecting something to be brought up at the last minute. It is, after all, the Democratic Party’s modus operandi. In the case of Clarence Thomas, it looked like the hearings were done and the nominee on the way to confirmation, when there was suddenly leaked an FBI report touching on Anita Hill’s allegation of sexual harassment.

Something similar happened in respect of Justice Kavanaugh. His four days of hearings were finished, and he, too, appeared on the road to confirmation when Senator Dianne Feinstein finally aired the allegation of the judge’s alleged misbehavior with a young woman at a party decades earlier. In both cases, the nominees were suddenly in doubt.

That is no doubt the moment the Democrats are reaching for with the surfacing, at the last moment, of two new pieces of evidence. One is from part of John Bolton’s draft memoir. The Times reports it suggests that in August Mr. Trump told his then-national security adviser that he wanted to hold $391 million of security aid against Ukraine’s help with a probe of the Bidens.

The other appears to be a cellphone recording of Mr. Trump meeting in 2018 with a group of donors that included Lev Parnas, an American businessman and crony of Mayor Giuliani. It captures Mr. Trump being told that his envoy to Ukraine has been predicting the President would be impeached and Mr. Trump responding, “Get her out tomorrow. I don’t care.”

That any of this evidence would be dispositive on the charges being heard in the Senate strikes us as unlikely. It looks, though, like an effort is underway to use the evidence to try to blow up the impeachment trial. No less a figure than President Obama’s erstwhile acting solicitor general, Neal Katyal, is out with an op-ed piece today in the Times suggesting turning to Chief Justice Roberts.

Mr. Katyal argues that under Senate rules Chief Justice Roberts — who, the Constitution itself ordains, presides when a president is tried in the Senate — has his own authority to subpoena evidence. Mr. Katyal recommends the Chief Justice do so, whatever a majority of the Senate might want. The idea seems to be that the evidence is so powerful that the Senate will be swayed.

That strikes us as a long shot. The purely partisan basis on which the House handed up its charges — nary one Republican vote — itself creates doubt, a point made in the Clinton impeachment trial in 1999. That’s impeachment 101. Plus, too, Mr. Trump would be fully justified in cashiering an envoy who is undercutting the president he or she represents.

As for Mr. Bolton’s memoir, our sense of the situation is that it wouldn’t matter whether Mr. Trump used foreign aid to pressure Ukraine into looking into the Bidens. That’s because it would be the right thing to do if Mr. Trump had genuine concerns about corruption. And what kind of president would look at the Biden situation and not at least have questions?

In any event, this kind of desperate, last minute effort to upend a proceeding that appears to be going in a direction the Democrats don’t like, well, it’s the Democrats’ m.o. That it failed twice, and left a trail of bitterness, apparently hasn’t stopped the Democrats. They just don’t want to leave the question of Mr. Trump’s presidency to the voters.