Some Republican conservatives have been threatening to back a third-party candidate for President next year if Rudy Giuliani wins the GOP nomination. Yet the sometimes-liberal former New York City mayor continues to run at or near the top of polls of Republican voters. When do parties reach outside the box for candidates? Do they define the people they nominate--or can a candidate change his party?
Desperation in politics can sometimes cause a major party to look outside its ranks for a standard bearer. In the presidential election of 1812, the Federalists, the strong-government party of the founding era, backed an earlier...