Judges are supposed to be impartial. How does donating to their campaigns enhance free speech?
Yes. Judges are intended to be impartial arbiters of the law.
How does donating to their campaigns enhance free speech?
Bans on Free Speech should restrict no more speech than necessary to achieve a compelling government objective. I'm not sure what objective you seek to achieve with your proposal to restrict Free Speech, but Justice Scalia discussed this principle just last week in Williams-Yulee v. Florida Bar:
before one can tell whether that interest is compelling and whether the speech restriction narrowly targets it. In White, for example, the Court did not allow a State to invoke hazy concerns about judicial impartiality in justification of an ethics rule against judicial candidates announcing their positions on legal issues.
And, for the sake of argument, lets say you can provide some sort of workable vague justification to restrict speech and can even conjure up some evidence that your speech prohibition would actually cause the positive effect you seek, your objection to Free Speech is so broad that it would still be unconstitutional. You'd catch someone who wants to donate to a law school classmate or someone who likes the judge's broad judicial philosophy in your blanket ban on speech.
I encourage you to read Williams-Yulee v. Florida Bar. Even the majority did not find that campaign donations to judicial candidates should be prohibited. But Justice Scalia's spirited dissent in Williams-Yulee provides a forceful case that campaign contributions to judicial candidates is protected Free Speech.