On Thursday, Barack Obama announced that his campaign was moving into a new phase. And, as the first part of that "new phase," he apparently took to heart the advice of much of the press corps and went after Hillary Clinton by name -- in this case for her vote designating the Iranian Revolutionary Guard as a terrorist organization

This is exactly what he should not be doing.

The Obama campaign does need to draw distinctions between its candidate and the front-runner. But it seems unable to understand that this election is never going to be decided by who or who didn't want to authorize the war back in 2002, or who's voting for what now - especially since Obama happened to miss this latest vote because he was apparently busy campaigning. These are distinctions without a difference unless he can point to very specific ways they will make an Obama America different from a Hillary America. Saying you're against "power over principle" and a "blustering foreign policy" don't cut it.

Far more important, Obama is undermining the premise of candidacy. He's promised to bring America together with a new kind of politics. Attacking Hillary is "politics as usual" -- and her campaign had no trouble pointing that out almost within seconds after he'd delivered his remarks.

What Obama needs to do is to draw clear differences without attacking his opponent. The way to do that is by showing how an Obama America would be different from Bill Clinton's America. Yes, Democrats are proud of Bill but there's a lot that he did and stood for that they would also like to change. Hillary can't disassociate herself from Bill: By subtly contrasting his hopes for America with the prior Clinton Administration's aspirations, he draws the necessary distinctions in a positive way, without mentioning her by name. (In fact, he doesn't even have to mention him either).

Obama has to make voters want to turn the page on both Bush and Clinton. Sure, it's easier said than done. But this, in fact, is his only path to victory.