At some point, after the election, Republicans will also need to ask themselves some tough questions about how their actions and inactions made the party vulnerable to Trump. After all, a candidate spewing anti-immigrant, anti-Muslim, authoritarian rhetoric didn’t come out of nowhere; the Tea Party has been strong enough long enough that someone like him shouldn’t be a surprise. Chasing short-term political gains, the GOP missed a lot of chances to fight the hateful currents that now threaten to overwhelm it.

For now, Republicans ought to focus on doing the right thing: putting up every legitimate roadblock to Trump that they can. Unexpectedly, a key moment in American democracy has snuck up on the GOP. When he denounced Trump, Romney said he wanted to be able to say he’d fought the good fight against a demagogue. That’s the test other Republicans may want to consider.

Action doesn’t mean political chicanery or subterfuge. It doesn’t mean settling for an equally extreme — and perhaps more dangerous — nominee in Ted Cruz. If the party can muster the courage to reject its first-place finisher, rejecting the runner-up should be even easier.