Sens. Lisa Murkowski (R-AK) and Susan Collins (R-ME) pitched President Donald Trump’s lawyers a curve ball Wednesday, asking a question that underscored the political motive behind Trump’s sudden interest in Ukrainian corruption.

The senators asked if Trump ever mentioned the Bidens in connection to corruption in Ukraine before the former Vice President announced his candidacy for president in April 2019.

Deputy Counsel to the President Patrick Philbin struggled to defuse the loaded question, spending some time explaining that his knowledge of what the President said comes only from the House’s limited inquiry and that some points were not “thoroughly pursued” in the record (he did not elaborate that the record was so curtailed because of the White House’s blocking of key administration figures from testifying).

Philbin eventually answered: “…I can’t point to something in the record that shows President Trump at an earlier time mentioning specifically something related to Joe or Hunter Biden.”

Philbin quickly pivoted to smearing the Bidens and rehashing Rudy Giuliani’s fact-finding mission.

The question, coming from those two senators, is significant. Trump’s alleged passion for cleaning up Ukrainian corruption has been a frequent defense from his lawyers by way of explaining why he held up the military aid. The query shows that these two lawmakers may not be buying it.

And while guessing at the thoughts behind the senators’ questions involves some measure of tea-leaf reading, this exchange reveals at least that they are actively engaging with testimony about Trump’s nefarious motives and willing to ask the President’s team unflattering questions.

For Republicans hoping to keep the caucus unified when it comes time to vote on witnesses, this small measure of rebellion is surely worrying.