Conor Friedersdorf, The Atlantic:
If a candidate who was clearly more conservative than Trump ran, he or she might attract support even from folks who now feel that a third-party bid is foolish strategy. Other factors that could help bring about such a challenge include the following:
In some states, a right-of-center electorate divided between Trump and a conservative challenger could turn out more total voters who’d support down-ballot Republicans than a Trump vs. Clinton race where conservatives stayed home.
If Trump wins, there will be a lot of establishment campaign professionals who’d benefit financially from a third-party challenge by a movement conservative (and who wouldn’t fear being branded disloyal for staffing one).
Many neoconservatives would prefer an Israel-loving, interventionist hawk like Hillary Clinton to Donald Trump, but also value their place in the conservative movement. Supporting a third-party challenge by a hawkish conservative would be much less disruptive to their network of alliances than openly supporting a hawkish Democrat, even if the likely outcome is the same. A third-party challenger could conceivably draw support both from coy Hillary Clinton Republicans and earnest haters of Clinton and Trump.
Right now, we’re seeing Trump in a Republican primary. He is more deferential to the conservative movement now than he would be in a general election—and he’s already breaking with party orthodoxy on health care, entitlements, Planned Parenthood, and foreign policy. I don’t know exactly what he’d say in a general election, but at some point, the faction of the GOP that’s spent 8 years obsessed with ideological purity will rebel. Like Erickson, they’ll argue that it’s better to go down fighting as conservatives than to compromise their values. Intransigence is consistent enough with their preexisting beliefs and past behavior to make me believe they’d abandon the GOP for the right candidate.