What does taking responsibility mean (in politics)?

You often hear it on the news. Some embarrassing nonsense goes down, and then some honcho steps in front of the cameras looking concerned and goes, "I take full responsibility for what happened."

What do they mean by that, exactly? Are they willing to be put on trial? Ready to pay a fine? Eager to resign? Do some community work for free? What?

I believe I've heard the President, and some others in high positions, say it on a few occasions. What do they mean when they say it?

Today I want to say this, as president and as Commander in Chief I take full responsibility for all of our counter terrorism operations including the one that inadvertently took the lives of Warren and Giovanni.

President Obama from the White House (Here's the link)

Generally, it's just political rhetoric used to try and defuse a situation. Denying responsibility often causes an issue to perpetuate. By someone saying they're "taking responsibility," there's no longer a witch hunt, no longer a back-and-forth dialogue. What's left to say after someone says, "Yes, I'm responsible for that?" Nothing. It's an especially good tactic when taking responsibility results in no real negative consequences, even possibly going the other way to make the confessor look magnanimous. Basically, what they mean is they want to put it to bed and stop hearing about it.