President Obama said that those Republicans who have repeatedly denounced Donald Trump’s comments should not be supporting his presidential campaign. On this point, I agree with him. But it’s worth noting that if Republicans had done what he suggests — or were to do it now — he would almost certainly move the goalposts. If Republicans don’t want him to be president, Obama would say, why don’t they just endorse Hillary Clinton?
Our political debate does not lack for (mostly liberal) voices that say that opposition to Trump is ineffectual and even hypocritical unless it includes an endorsement of Clinton, just as it does not lack for (mostly pro-Trump) voices that say that opposition to Trump amounts to an endorsement of Clinton. Both conclusions seem to me to be based on an incorrect view of voting for president. The main question someone voting for president should ask himself is, Whom do I will to be president? Under normal circumstances, when at least one candidate satisfies the threshold conditions of fitness for office, that question reduces to the question, Whom do I prefer to be president? When those circumstances do not obtain, however, no individual voter has any moral obligation to reach an answer to the question of preference, let alone to cast a vote based on that answer.
Matthew Franck has developed a longer version of the argument about how we should act in this situation.
Obama's Challenge to Republicans