The gloves have come off. Calling Donald Trump ‘unfit’ to be president, Barack Obama has called on top Republican leaders to withdraw support for their nominee. The G.O.P. elite has yet to denounce Trump outright, though many from Paul Ryan to John McCain have responded strongly to his recent attacks on the family of a Muslim-American soldier who died in Iraq. The president called Republicans’ criticism of Trump “hollow” without action: “If you are repeatedly having to say in very strong terms that what he has said is unacceptable, why are you still endorsing him?” Obama said.