We all know that President Obama believes in evolution.
Specifically, he believes in the evolution of his positions on political issues, like gay marriage. Before he was a U.S. senator, Obama liked gay marriage. Then, when he ran for the Senate, he said gay marriage was wrong. As president, he claimed his views were "evolving" on it -- and finally, this week, after Vice President Joe Biden jumped the gun, Obama said he likes it again.
Curiously, Obama's reversal was described in most places as the completion of his evolution, an unprecedented declaration -- not a flip-flop.
"It was called a historic decision in most of the media," laughed Ari Fleischer, one of George W. Bush's press secretaries.
So what's the difference between an evolution and a flip-flop?
Go back eight years to the 2004 campaign between Bush and John Kerry. The Democratic candidate was hounded throughout the campaign for being a "flip-flopper," someone who changes his positions depending on how popular they are at the time.
His most damning quote: "I actually did vote for the $87 billion before I voted against it."
Flip-flops came to be defined in that campaign as 180s on such politically expedient issues as supporting the war in Iraq, the Patriot Act, affirmative action and No Child Left Behind.
Now the term is flopped around for pretty much every slight deviance or half-pivot on an issue, perhaps removing some of the sharpness it once carried.
But there are still real flip-flops that get plenty of attention. Mitt Romney, for example, has switched his positions entirely on abortion and gay rights.
So why aren't those reversals characterized as the more euphemistic evolutions?
One person who worked on Kerry's 2004 campaign said the difference lies in whether the policy change helps the candidate. Romney was trying to appeal to a different voting crowd when he swapped his pro-choice views for pro-life, whereas Obama was more or less forced by his unleashed vice president to come out in favor of gay marriage before he wanted to.
"What John Kerry was accused of was changing positions in the middle of a campaign for political expediency," the ex-campaign aide said. "If Barack Obama had [Wednesday] attempted to explain away a shift that clearly was a play to gain votes, it would've been a higher hurdle for him to get through."
Fleischer has another explanation: good old-fashioned bias in the liberal media.
"If the press agrees with your latest position, it's a historic decision, and they accept the definition of evolution," he said. "If the press doesn't like or is uncomfortable with that position, it's a flip-flop."
Media bias is a tricky arena. Fleischer says most political journalists in the mainstream media acknowledge that their personal views lean toward the liberal side, but say they don't let their opinions interfere with their work.
Fleischer said his longstanding thesis is that those views do matter, and that as human beings, journalists allow their feelings to seep into their approach to their job.
"Romney flip-flopped on abortion and gay rights, but so did Barack Obama," he said. "Romney changed positions in order to run for president. So did Barack Obama."