In Gettysburg, Pa., on Tuesday night, Rick Santorum stood on the grounds where more lives were lost than in any other Civil War battle, and where Abraham Lincoln issued his stirring call for unity and democracy. Mr. Santorum, who had just lost the Republican primary in Illinois, called the presidential race the “most important election since the election of 1860.”

Numbers like 1776 and 1860 increasingly pepper his speeches as he stresses the historical urgency of his candidacy. He speaks of his campaign as bearing a torch of freedom and honor first lighted by the signers of the Declaration of Independence. While his supporters need not risk life and fortune as John Hancock and his compatriots did, Mr. Santorum tells his audiences, they can fulfill their own duty by posting pictures with the candidate on Facebook.

As he traveled around Illinois, Mr. Santorum cast himself as the defender of America’s history....