Ted Cruz, playing dirty tricks during an election? Say it ain’t so!

Over the past few weeks, Mr. Cruz’s GOP opponents have worked themselves into a lather of right-wing indignation over his underhanded tactics. As Mr. Cruz admitted, his campaign spread false rumors that Ben Carson was dropping out of the race. The campaign also distributed a video that purported to show Marco Rubio doubting the Bible, which led Mr. Cruz to fire his communications director.

But here’s one thing you won’t hear Mr. Cruz’s foes say: Dirty tricks have become a hallmark of the modern Republican Party. Over the past half-century, the GOP has perfected the dark art of the underhanded smear.

It used to be a much more bipartisan tradition. In the 19th century, Democrats insinuated that Abraham Lincoln was secretly black. They did the same thing to Warren Harding in the 1920s. And Franklin D. Roosevelt instructed his aides to spread rumors about marital infidelity by his 1940 Republican opponent, Wendell Wilkie.

“Spread it as a word-of-mouth thing, or by some people way, way down the line,” said FDR, who was carrying on his own extra-marital affair. “We can’t have any of our principal speakers refer to it.”

Likewise, Lyndon Johnson and his close advisers didn’t smear Barry Goldwater directly in 1964. They left that to an army of low-level operatives, who, among other things, wrote anti-Goldwater letters to Ann Landers under false names. They even put out a children’s coloring book that featured Goldwater dressed in Ku Klux Klan robes. ...