Inside the Mansfield Room at the Capitol, where Senate Republicans have held daily strategy sessions during President Trump’s impeachment trial, senators began walking through their arguments on why they should block witnesses from testifying in the proceedings. But at this lunch on Thursday, Sen. Mitt Romney (Utah) was getting visibly annoyed. If this is meant to persuade me, Romney told his colleagues, it’s not helpful, according to two officials with knowledge of the exchange. The senator, a near-lone GOP voice in seeking witnesses for the trial, felt as if other Republicans were singling him out.... Trump’s acquittal was never in...