The question from last week’s sudden shift in momentum towards Herman Cain in the GOP presidential primary race was whether Cain could actually vie for the nomination.  After today’s poll from the Washington Post and ABC, the question may be whether anyone but Mitt Romney could stop him.  Right now, it certainly doesn’t like Rick Perry could, whose fortunes have fallen faster than they rose after two bad debates:

After a quick rise in the race for the Republican presidential nomination, Texas Gov. Rick Perry has experienced an almost equally dramatic decline, losing about half of his support over the past month, according to a new Washington Post-ABC News poll.

Perry’s slide, which comes after several uneven performances in candidate debates, has allowed former Massachusetts governor Mitt Romney to resurface atop the GOP field. But the most direct beneficiary of the disenchantment with Perry is businessman Herman Cain, who is now tied for second place.

You know who this, er, doesn’t help?  Oddly enough, Sarah Palin and Chris Christie:

Christie is feverishly assessing whether to do so, with a decision expected this week. But the Post-ABC poll finds only modest public support for a Christie candidacy. About 42 percent of Republicans and GOP-leaning independents say they would like to see the New Jersey governor join the race.Thirty-four percent, say no, with the rest offering no opinion.

That finding is far more positive than the receptivity to a candidacy by Sarah Palin. Two-thirds of Republicans say they do not want the former Alaska governor to seek the party’s nomination.

There is plenty more to this poll in the GOP race, but let’s shift to Barack Obama for a moment.  The buzz over Cain’s sudden momentum will obscure the fact that Obama gets the lowest job-approval rating in the WaPo/ABC series at 42/54, which is also the highest disapproval of the series.  A month ago Obama was at 43/53, and he launched his new hard-Left populist strategy, along with a jobs bill and a deficit-reduction proposal.  Both seem to have flopped — even with a sample tilted toward Democrats at 32/25/37.

Oddly, Obama falls into virtual ties with Romney, Perry, and Christie among registered voters, but an overwhelming majority expects Obama to lose next year, 55/37. Among registered voters, 46% say they will definitely not vote for Obama next year, while only 23% say they definitely will — a slight improvement over August’s results.  Also, for all of the media talk about the collapse in polling for the Tea Party, the WaPo/ABC poll shows support at 42/47, not terribly different from its track all year long, and slightly better than April’s 42/49.

Back to the horse race.  The rankings don’t change when narrowing the respondents to registered voters, with Romney leading, Cain and Perry tied for second, and Christie in fourth place to close out those in double digits.  Palin and Ron Paul are tied among general-population respondents, followed by Newt Gingrich and then Michele Bachmann, with Rick Santorum and Jon Huntsman at 1% each — which might put both out of the next debate.  The order doesn’t change at all with Palin out of the mix, or with Christie out of the mix, either.

The big news here is Herman Cain, especially among those to whom he is news.  He easily gets the best score among the contestants on the question “the more you hear about X, do you like him/her more or less?”  Cain gets at 47/12 on that question, while Romney gets a 38/35 and Perry gets a red-flag 30/44.  Christie comes close to Cain in this category at 43/23, but Palin’s closer to Perry at 35/49.

Cain appears to have caught fire, but as we saw with Perry, all that means is that the scrutiny of the media — and the other candidates — will now turn to Cain.  We’ll see how well he handles the heat, but another good debate performance might push him into the leading Not-Romney slot in the race.