FRESNO, Calif. — Fighting to retake his blue-leaning seat two years ago, Rep. David G. Valadao (R-Calif.) had to ward off accusations he was a “yes man” for former president Donald Trump. In ads, the Republican touted his role in a bill signed by another ex-president: Barack Obama. But this year, running in an even bluer district that is seen as one of the election cycle’s most competitive, Valadao is doing little to communicate one defining show of political independence — his vote to impeach Trump. “There’s actually no point in talking about it, because so many people know about...