Six months after Barack Obama's inauguration, a persistent and noisy legion of doubters won't let go of an already debunked claim — that he is actually a foreign-born, illegal president. Mainstream Republicans who want the issue to go away are having a tough time stamping it out as the so-called "birthers" resurface, with assists from talk show host Rush Limbaugh and CNN's Lou Dobbs. Passions among the birthers run so high that Rep. Mike Castle, R-Del., was booed by his own constituents at a recent town hall meeting for saying Obama "is a citizen of the United States." He was...