This month marks the 40th anniversary of an event so unexpected that it created a phrase that’s become part of our political lexicon: The shorthand is “Nixon goes to China,” meaning a moment in which a leader reverses his past positions to do something that is shocking but beneficial.

Richard Nixon is hardly a role model, overall; he was a devious president who encouraged illegal actions by his subordinates. But he was a clever strategist — never more so than in the opening to China that culminated in his February 1972 visit to Beijing. Yet even Nixon, the practiced hypocrite, might not dare to buck conformity today.

Doing the unexpected is almost forbidden in American politics these days. The invisible thought police that govern our public space treat any deviation from past policy positions as a flip-flop or, worse, evidence of a character flaw. We pretend that good politicians are the ones who think the same thing, always, forever.

Politicians today are expected to do precisely what they have promised, like contract laborers. Newt Gingrich promoted this politics-as-straitjacket notion with his 1994 “Contract with America.” His GOP heirs in Congress sometimes act as if they’re ready to run the country off a cliff, to keep their campaign promises.

Mitt Romney’s biggest problem has been his contortions in denying the obvious fact that he’s a flip-flopper. By pretending that his Massachusetts health-care reform wasn’t a model for President Obama’s plan, he trivializes his own achievement and makes himself look like a phony, to boot.

So here’s a salute to inconsistency, cunning and other un-American traits that made Nixon’s opening to China possible. As we approach this week’s anniversary of his departure for Beijing, it’s useful to look back at one of the biggest — and best — flip-flops in American history.

Nixon arguably was the only U.S. politician who could have gotten away with such a bold move. He had the right-wing credentials, as an anti-communist and advocate of Taiwan. A typical Nixon blast was his 1964 comment during a trip to Asia that “it would be disastrous to the cause of freedom” for the U.S. to recognize Red China, which is precisely what he ended up doing.

Nixon was struggling abroad as he contemplated the China move: He was bogged down in a deeply unpopular Vietnam War and looking for new ways to contain the Soviet Union. Working with his brilliant and ambitious national security adviser, Henry Kissinger, Nixon let himself think the unthinkable.

It’s interesting, looking back, to see how carefully Nixon prepared the way. In April 1971, he approved a trip to China by the U.S. national pingpong team, announced a plan to ease travel and trade restrictions, and said that one of his long-term goals was the normalization of relations with China. The Chinese responded that spring, through Pakistan, that Nixon himself would be welcome in Beijing. Nixon initially sent Kissinger instead, on a July 1971 secret mission that was facilitated by the Pakistanis. According to Nixon biographer Stephen Ambrose, Kissinger sent a one-word coded message that his mission had succeeded: “Eureka.”

Nixon announced Kissinger’s mind-boggling trip on television with what, in retrospect, was a comforting lie: He said that the opening to China “will not be at the expense of our old friends” in Taiwan.

Nixon departed on his own journey to Beijing on Feb. 17, 1972. His words to Mao Zedong, quoted by Ambrose, are a testimonial to the value of changing course when it’s advantageous to do so: “You are one who sees when an opportunity comes, and then knows that you must seize the hour and seize the day,” Nixon said, paraphrasing Mao’s own words. The statement was just as true of Nixon.

Before leaving China on Feb. 28, Nixon said at a banquet in his honor: “This was the week that changed the world.” That was a bit of Nixonian amour-propre, but he was right.

Great presidential decisions are often ones that escape the boundaries of what a leader may have said in the past, or what his political advisers recommend, or what the conventional wisdom of the day seems to supports. That was true of Nixon in China, Kennedy in the Cuban missile crisis, Roosevelt in the Great Depression, Lincoln in the Civil War.

The leader who can deal with America’s problems today may be the one who’s ready to respond to complaints that his policies go against past positions with a simple statement: So what? I’m doing what’s right for the country.