Republican Rep. Duncan D. Hunter is running a brazenly anti-Muslim campaign against his Democratic opponent, a Christian who is the son of a Mexican-American mother and Palestinian father. The ugliness has unfolded in one of the most conservative congressional districts in California, where Hunter, a hard-charging former Marine who served three combat tours in Iraq and Afghanistan, is trying to hold on to his seat after being indicted on federal corruption charges for the alleged misuse of campaign funds.