During last night's debate, Obama had this to say about his PA "elitist" gaffe.

So the problem that we have in our politics, which is fairly

typical, is that you take one person's statement, if it's not properly

phrased, and you just beat it to death. And that's what Senator

Clinton's been doing over the last four days.

And I understand that. That's politics.

Today Obama said that Clinton was "in her element" last night.  Obama likes to claim, and many of his supporters believe, that he only defends himself when it comes to these non-issues he didn't want to address last night.  That he would never go on the attack against a fellow Democrat.

He, of course, is lying.  Remember this?

Barack Obama’s campaign has debuted a new radio ad in Mississippi
called "Respect," highlighting what they call “derogatory” remarks
Hillary Clinton made about the state late last year.

The ad also argues that Obama will “practice his Christian faith by
respecting us” — an apparent push-back against the false Muslim rumors
that have dogged him throughout the campaign.

In the 30-second spot, former Mississippi Governor Ray Mabus, an
Obama supporter, derides Clinton for comments she made last fall
singling out the state’s record of electing female politicians.

"I was shocked when I learned Iowa and Mississippi have never
elected a woman governor, senator or member of Congress," Clinton told
the Des Moines Register in October. "There has got to be something at
work here. How can Iowa be ranked with Mississippi? That's not the
quality. That's not the communitarianism, that's not the openness I see
in Iowa.'"

Mabus accuses the Clinton campaign of calling Mississippi voters “second class.”

link

Why is it OK for Obama to take people's gaffes and run ads to capitalize on them, but when Clinton does it it's "old politics"? 

Why does he think he doesn't have to answer to the same standards he holds other people to?