On Oct. 12, 1948, the campaign train of Tom Dewey, the Republican nominee against President Harry Truman, pulled into Beaucoup, Ill., where, from the rear platform, he would speak to about 1,000 people. Before he began, the engineer mistakenly caused the train to lurch a few feet backward, frightening some but injuring none.

Dewey, however, hurt himself by angrily saying into the microphone, “That’s the first lunatic I’ve had for an engineer. He probably ought to be shot at sunrise.” Dewey’s “cold arrogance” (Truman biographer David McCullough’s description) reinforced the public’s impression of an unsympathetic and prickly politician.

So, small vote totals for independent candidacies can have huge potential consequences. Which brings us to Ron Paul.

When recently asked if he might mount an independent candidacy, he said: “I’m not thinking about it because, look, I’m not doing badly right now. . . . So we concentrate only on one thing: Keep moving up in the polls, and see how things come out in a month or two.”

He is in the top tier in Iowa and would alienate Republican voters if he indicated an interest in bolting the party next autumn. Nationally, his ceiling is low, but his floor is solid: His supporters are inclined to accept no substitutes because no other candidate espouses anything like his high-octane blend of libertarianism and isolationism.