Campaigning in the City of Brotherly Love, Sen. Hillary Clinton says she’s got this in common with legendary film boxer Rocky Balboa — she’s no quitter.

Recalling the famous scene on the steps of the Philadelphia Museum of Art from the 1976 Oscar-winning film Rocky, Clinton said ending her White House bid now would be the same as if “Rocky Balboa had gotten halfway up those art museum steps and said, ‘Well, I guess that’s about far enough.’”

“Let me tell you something, when it comes to finishing a fight, Rocky and I have a lot in common. I never quit. I never give up. And neither do the American people,” Clinton told the Pennsylvania AFL-CIO at a campaign event.

Clinton warned that Democrats won’t have an easy time against GOP nominee John McCain in November’s general election, and implied that her rival for the Democratic nomination, Sen. Barack Obama, may not be up to the task.

“The Republicans are not going to give up without a fight,” Clinton said. “And no matter how beautiful your rhetoric, the Republicans aren’t going to turn off their attack machine — it doesn’t have an off-switch.”

UPHILL BATTLE: Hillary Clinton fashions herself as a political Rocky Balboa.

In recent days, Clinton has made an issue of calls from some Obama backers for her to abandon the race. Even some Clinton supporters have argued that simple math makes a win impossible for her and she’s only hurting the nominee.

For his part, Barack Obama will not go along with other Democrats calling for Clinton to drop out, saying Saturday on the campaign trail that “My attitude is Senator Clinton can run as long as she wants.

Subtly or otherwise, Obama supporters Bill Richardson, Chris Dodd and Patrick Leahy, along with the supposedly neutral Harry Reid and Nancy Pelosi, have all made statements to the effect that Hillary should bow out.

Much as we would prefer our candidate of choice to wrap it up sooner rather than later (it’s human nature), we also understand the argument that Hillary Clinton staying in the hunt, at worst, is making Barack Obama a better candidate.

As of now, it appears Obama weathered the Rev. Jeremiah Wright blow up. His “A More Perfect Union” speech was a defining moment, one that shifted the debate from one man’s values to a broader discussion about race and society.

For many Democrats, it was a leadership moment, one that weakened Obama but didn’t kill him, and thus made him stronger down the line. And one which, it stands to reason, wouldn’t have occurred without Clinton in the race.