They don't have one, and they can't stop Trump. They just have to hope that he implodes. If Trump actually wins the nomination, the Republican Party will actually just get worse (just like Goldwater pushed the party to the right, Trump will push it in a different direction). They will become a protectionist party, centered around nationalism and nativism. No longer a party of big business, but a party that serves the interest of the native population and its 'national interest' abroad.
"Worse".
That's my opinion, but yes its the worst possible direction to take electorally. The young, urban, black, Hispanic, Asian, non-religious, etc. All groups that are growing in the electorate and/or in population, are going to overwhelmingly reject the Republican Party (even more than before) and its going to keep losing.
The fact is that Mitt Romney would have had to do 45 points better with Hispanics to win in 2012 as opposed to just 4 points better with whites. So what's the strategy to entice asians, blacks, hispanics, and atheists into a political party that the overwhelming majority of them instinctually fear and loathe?
Mitt Romney could've won 45% of the Hispanic vote and won with 49% of the vote (with everything else staying the same). And Mitt Romney could've also won with 49% if he got 40% out of both Hispanic and Asians. But anyway, the party can stop instinctively fearing and loathing them. That would be a great start! And forget atheists, the broader non-religious group is what the right ought to be worried about, atheists are overwhelmingly left wing as a group.
A point oft-forgotten, I think. A lot of people are apathetic about religion or just non-believers, period, but not as militant (or annoying) as atheists. The political evangelicalism of many (particularly Southern) Republicans is exactly why these people don't vote GOP, even though a lot of them could probably be corralled into the center-right tent on economic issues.
