Eric Fehrnstrom and David Axelrod are two of the most important political advisers in America. They are grown-ups. But they are engaged in an ongoing war of words on Twitter that can only end with one declaring : “I know you are, but what am I” and the other retorting: ”I’m rubber, you’re glue.”

The latest round came this morning when Axelrod, a former White House adviser to President Obama and now a key force running his re-election campaign, sent a tweet exclaiming:

“A year ago, Romney hit Obama in No Apology for being too tough on China. Now Mitt’s a trade warrior? Should have called his book ‘No Shame!’”

That elicited a response from Fehrnstrom, a longtime adviser to Romney, who shot back at ”@davidaxelrod: You should rename Obama’s book ”The Audacity of Indifference’ or ‘How I Golfed My Way Through a Recession.””

Hey, if you can’t have a direct debate between the candidates, or even a face-to-face exchange between advisers, what’s better than a volley of insults in 140 characters or less?