Comparing a political figure to Adolf Hitler may be the worst thing one could say about any political candidate, but it is nothing new.

For his extreme anti-migrant talk regarding Mexicans and Muslims, leading GOP candidate Donald Trump has been compared to Hitler by people as disparate as comedian Louis C.K. and Mexican President Enrique Pena Nieto.

To put these recent remarks in context, here are a few times in recent history when political figures have been compared to the Fuhrer.

Richard Nixon

In 1971, the year before the Watergate scandal, President Richard Nixon was described by his Democratic rival George McGovern as a warmonger like Hitler.

"Except for Adolf Hitler's extermination of the Jewish people, the American bombardment of defenseless peasants in Indochina is the most barbaric act of modern times," said McGovern.

After the arrests of the five agents who broke into the Democratic National Committee headquarters, McGovern said Nixon’s involvement in the Watergate break-in was "the kind of thing you expect under a person like Hitler."

Ronald Reagan

In 1983, Cuban President Fidel Castro denounced the U.S. invasion of Grenada and compared Ronald Regan’s administration to Hitler’s regime, while describing the American people as similar to German citizens under Nazi rule.

The communist leader said the American people were being ''grossly manipulated by their government as the people were in the era of German Fascism.''

George W. Bush

In 2004, the leftist group MoveOn.org was taken to task for running ads that compared Bush to Hitler. Virginian Rep. Eric Cantor found the group's comparison of Bush to Hitler exploitative and offensive.

“I’m disgusted by the casual use of Hitler by liberal Democrats and groups such as MoveOn.org,” Cantor said. “To compare any American president, much less George W. Bush, to Adolf Hitler, cheapens the sacrifice of millions of lives that have been lost by this country over its history and really denigrates the efforts by the American military.”

Barack Obama

In 2007, presidential hopeful Mike Huckabee likened Obama’s foreign policy to Hitler’s planned extermination of European Jews.

“This president’s foreign policy is the most feckless in American history," said the former preacher turned politician. "It is so naive that he would trust the Iranians. By doing so, he will take the Israelis and march them to the door of the oven.”

Godwin’s Law

Writer and attorney Michael Godwin has tracked the phenomena of Internet groups using Nazi analogies to disparage public personalities since the 1990s. Although he sees the overuse of the Nazi comparison as hyperbolic and ultimately ineffective, he believes the insulting comparison is OK, so long as it is informed by a real understanding of historical events.

“If you’re thoughtful about it and show some real awareness of history, go ahead and refer to Hitler or Nazis when you talk about Trump. Or any other politician,” Godwin said.

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