McCain frequently cites Theodore Roosevelt as his hero, the trust-busting maverick with a distinguished military record and progressive tack. Given the comparison, it’s worth drawing a rough analogy.
Roosevelt’s Oval Office successor William Taft swung back to conservative principles, creating a schism in the Republican party. The two presidents’ competing philosophies each attracted a separate wing, not unlike the split between the hard-right and center-right brewing today.
Due to Taft and Roosevelt’s bitter political feud, the Republicans eventually split into two, as Roosevelt left to form the Progressive (Bull Moose) Party. The election of 1912 featured a three-way race between incumbent Taft, Roosevelt, and Democrat Woodrow Wilson. Wilson won resoundingly, capturing 435 electoral votes; even in a two-man race, historians argue he would have won because the Republican factions would not support each other.
The current Republican party splintering into two may be an extreme situation, but as First Read writes:
Win or lose in November, the GOP is going to go through an identity crisis. And especially if McCain loses, it’s going to be one ugly period in the history of the Republican Party.