An ABC News poll finds that most Americans oppose gay marriage but markedly fewer — especially those outside George W. Bush's core supporters — would amend the U.S. Constitution to ban it. Opponents, however, are far more likely to call it a make-or-break issue in their vote for Congress — a finding that explains Bush's renewed push for a gay marriage ban. Among all Americans, 58 percent say gay marriage should be illegal, but fewer, 42 percent, say it rises to the level of amending the U.S. Constitution. Among conservative Republicans and evangelical white Protestants, though, opposition to gay marriage...