What their fellow extremists once called "Purges". Should the Republicans 'purge' their party of all but ideologues, their political fate will be determined: relugated to minority status for a generation or more.
OR the party could be switched out and either Libertarians come in (my preference) or Dems split and half of them become the new "other" party.
After all, that happened before, in Lincoln's time: the Whigs got switched out.
Of course, that was right before a Civil War, but that strikes me as VERY like what's going on today, massive national disunity.