NASHVILLE, Tenn. — U.S. District Judge Eli Richardson, a Trump administration appointee who bucked the president’s conservative base by blocking a Tennessee law that restricts mail-in voting, had an announcement to make before wrapping up his decision: it had nothing to do with politics.The declaration dropped as lower-court judges, like Richardson, face greater scrutiny over their perceived ideological purity. Richardson even took the step of addressing potential critics in his opinion.Richardson ruled in favor of …