Public Policy Polling’s latest Iowa survey provides more evidence that former Godfather’s Pizza CEO Herman Cain is gaining support among Republicans as Texas Governor Rick Perry and Representative Michele Bachmann lose ground.

PPP surveyed 311 “probable” Iowa caucus-goers between October 7 and 10, producing a statistical margin of error of plus or minus 5.6 percent. It’s not clear what likely voter screen was used in the automated phone calls. Click here for full results and crosstabs, including second choices for respondents and favorability ratings for all GOP presidential candidates.

Cain leads with support from 30 percent of respondents, followed by former Massachusetts Governor Mitt Romney (22 percent), Representative Ron Paul (10 percent), Perry (9 percent), Bachmann and Newt Gingrich (8 percent each), former U.S. Senator Rick Santorum (5 percent), and former governors Jon Huntsman and Gary Johnson (1 percent each). PPP’s Tom Jensen comments,

Perry and Bachmann have both collapsed, losing 13 and 10 points respectively while Paul is down 6 points and Huntsman is down 2 points as well.  […]

Better news for Cain even than his lead is that his supporters are much more solidly committed than Romney’s. 50% of them say they will definitely vote for him compared to only 34% who say the same for his co-front runner.  When you look at the race just among voters who say they are firmly committed Cain’s lead expands to 19 points at 38% to 19% for Romney, 13% for Paul, and 12% for Perry. […]

Cain’s building his lead off the most conservative elements of the Republican Party.  Romney actually leads with both moderates (25-23) and voters describing themselves as ‘somewhat conservative’ (33-22). But Cain is completely destroying Romney with ‘very conservative’ voters, 40-11, and that’s what gives him his overall advantage.

Cain is up 39-14 on Romney with Tea Party voters and digging deeper on those numbers you see one of the biggest issues Romney is having to contend with. 53% of Tea Partiers think Romney’s too liberal to only 36% who describe him as ideologically ‘about right.’ Cain has no such perceived ideological problem with those voters- 79% describe him as ‘about right’ to just 7% who think he’s too liberal.

Cain is a fantastic speaker, but he comes across as uninformed on many issues. Can he maintain a lead as he receives more scrutiny from the media? I suspect his 9-9-9 tax proposal will be less appealing to voters as they learn more about it. Conservative commentators are already noticing the political and substantive problems with the 9-9-9 solution.

While candidates appealing to the most conservative Republicans rise and fall, Romney has held steady around the low 20s in nearly every Iowa poll taken this year. It makes me wonder whether that’s his ceiling as well as his floor.

Perry’s collapse is striking, especially since three separate polls showed him leading among Iowa Republicans in late August and early September. I doubt you can pin that kind of slide on a few stumbling debate performances. Perry’s defense of giving in-state tuition to some undocumented immigrants seems to have hurt him badly. Several rival candidates have bashed Perry on the policy, which was uncontroversial when adopted 10 years ago in Texas. While I think this is one of the few things he’s right about, the Republican base disagrees. After the candidates debated in Orlando a few weeks ago, GOP pollster Frank Luntz said that when Perry defended giving in-state tuition for undocumented immigrants, his focus group’s reaction was one of the most negative he’d ever seen from a room of Republicans listening to a Republican.

While PPP’s latest Iowa poll was in the field, Perry made a campaign trip to northwest Iowa. He tried to keep his focus on jobs and reframe the immigration controversy in an economic context:

After an audience member asked about his support for in-state college tuition for illegal immigrants, Perry pivoted back to jobs. For the first time, he used a pro-growth defense of the 2001 law, overwhelmingly approved by Texas legislators. Back then, the border state had a choice of creating more taxpayers or “tax wasters,” he said.

“We could either kick them to the side of the road and say ‘We’ll deal with you as a tax waster or we’re going to give them the opportunity to pursue citizenship, to pay in-state tuition – full-fare, not subsidized in any form or fashion – and be part of an educated work force,” he told the audience.

Jim Cross said he was ready to give Perry another look after hearing the Texas governor explain that, rather than getting a “free ride,” children of undocumented workers pay the same tuition as other students attending public universities in the state.

“I like him more than I did an hour ago,” Cross, a Moville, Iowa, farmer, said of Perry. Prior to Saturday’s forum, Cross said he had been leaning toward Georgia businessman Herman Cain, who has been rising in the polls, largely at Perry’s expense.

The Des Moines Register’s Jennifer Jacobs went to Perry, Iowa to talk about how the immigration issue would play among GOP caucus-goers.

“If there is one thing that could cost Rick Perry potential support in the caucuses here, it would be that,” said Jeff Webster, sports editor at the weekly Perry Chief and a conservative Republican.

Immigration will be in the national spotlight this week with rival candidate Michele Bachmann’s visit to Perry, where she’s expected to continue to bash Rick Perry on his immigration record.

“Perry, Iowa, is dealing with the consequences of our weak immigration laws,” Bachmann campaign spokeswoman Alice Stewart told The Des Moines Register on Tuesday. “It’s fitting for Michele to go there and highlight her strong stance on immigration reform, which includes building a fence, enforce existing laws, no amnesty, and no magnets to lure illegals to this country.” […]

“What I think is kind of funny is Bachmann’s chosen Perry to diss Perry,” said Republican Mark Hansen, a county supervisor. “But she doesn’t have any understanding of what the Hispanic population has meant for Perry, Iowa.”

All those quoted in this article said that they believe illegal immigration is no longer a serious problem in Perry, and that they greatly appreciate the Hispanic families living here legally and contributing to the local economy and neighborhood life. Hispanics made up 35 percent of Perry’s population of 7,702 as of the 2010 census, up from about 2 percent 20 years ago.

No surprise that conservative dogma about DREAM Act policies and immigration as a whole bears no relationship to basic economic and demographic facts. The Bachmann campaign’s position makes no sense.

But Perry is under the most pressure to defuse this issue. Romney has a commanding lead in New Hampshire and could roll to the nomination if Perry can’t stop him in Iowa.

Final note on the new PPP poll: I was struck by the results for question 23, “Do you think Barack Obama was born in the United States?” For the full sample, only 37 percent of probable Iowa Republican caucus-goers said yes, 42 percent said no and 22 percent weren’t sure. Looking at the crosstabs (last page of this pdf file), you see a huge disparity depending on the respondent’s age. Among those between 18 and 29, 55 percent believe the president was born in the U.S., and for those between 30 and 45, the figure is 46 percent. About 38 percent of respondents between 46 and 65 said Obama was born in the U.S., while just 20 percent of those over 65 said so.

Share any relevant thoughts in this thread. I missed last night’s Republican debate in New Hampshire. If you watched, please let us know how you think the candidates did.

UPDATE: The latest nationwide poll of Republicans for NBC and the Wall Street Journal showed Cain leading Romney by 27 percent to 23 percent. Perry was third in that poll with 16 percent, followed by Paul (11 percent), Gingrich (8 percent), Bachmann (5 percent) and Huntsman (3 percent).

Among a full sample of respondents, President Obama’s approval rating was 44%, also unchanged from August; 51% disapproved of his job performance.

In hypothetical general election matchups, Obama leads Mitt Romney 46%-44%. The president fares far better against Perry (51%-39%) and Cain (49%-38%).

The national survey of 1,000 adults was conducted Oct. 6 through 10. The subsample of 336 Republican primary voters had a margin of error of 5.35 percentage points.

As I mentioned above, Cain hasn’t campaigned actively in Iowa during the past two months, but he says he will add staff in Iowa and New Hampshire for the final stretch:

“We have run this very lean by design. We are now going to ramp up,” he told reporters near the New Hampshire State House Wednesday afternoon. “We now have the money to do so. I didn’t want to get out in front and commit to spending a whole lot of money before I knew that the American people were going to say, ‘You know what? This long shot may not be such a long shot.'” […]

And in a race that has seen its share of shifting storylines, Cain insisted he’s not the flavor of the week.

“Haagen Dazs black walnut tastes good all the time,” he said with a smile.

Jon Stewart has been having fun with that “black walnut” tag line.

SECOND UPDATE: Anti-tax guru Grover Norquist has started criticizing Cain’s tax plan in media interviews. For instance,

“It’s like having three needles in your arm taking blood out. It’s much more dangerous than just one,” Norquist said on MSNBC.

Cain’s proposal would replace the current code with a 9 percent tax on all personal income, corporate income and sales. […]

“With the caveat that I understand this cry of rage that people have about the present structure and wanting to do something radically different, I’m much more comfortable taking the present mess and chipping away at it like an ice sculpture to get it down to what you want,” Norquist said. […]

“The good news is the next Republican president only needs a forefinger and then pen and the capacity to hold a pen, he doesn’t need to come up with ideas,” Norquist said. “We have a Republican House, we will have a Republican Senate, they will fix the tax code and send them stuff to sign. He can fly around in a cool big plane and hang around the White House and he can sign the legislation that [House Speaker John] Boehner and [Senate Minority Leader] Mitch McConnell send him, and we’ll be fine.”

Cain’s economic adviser Rich Lowrie discussed the 9-9-9 plan with Jennifer Rubin of the Washington Post.

His 9 percent sales tax has already been criticized by Santorum and conservative tax gurus. Lowrie says that the tax would have no exemptions. That means food, rent, everything would be subject to the tax. But doesn’t this sock it to the poor and middle class?

Lowrie insists it doesn’t because other “embedded” taxes (corporate taxes, payroll taxes) would be repealed. But most experts think the math here doesn’t work. Lowrie is unconcerned about the enforcement issues and the potential for off-the-books transactions. He insists that, with only a 9 percent rate, we could largely rely on “voluntary compliance.” He insists that politicians would find it hard to raise the sales tax because the rate would be clear to everyone. (Spoken like someone who’s never had a conversation with congressional Democrats.)

Cain’s plan is also vulnerable on the income tax side. After fencing with me for some time, Lowrie acknowledged that Cain didn’t care about progressivity. In devising the plan, Cain aimed for aimed for simplicity, transparency, and “fairness” (in the “Webster definition” sense, he says, meaning that income is taxed the same for everyone).

Lowrie says it’s just “Washington thinking” to look at whether modest-income Americans will wind up shouldering much more of the tax burden. He repeatedly refused to say how much more of the tax burden would be borne by the poor and middle class than under the current system. But he implicitly acknowledged the problem by saying that the campaign would “fix this” with a new empowerment-zone plan that would be laid on top of the 9-9-9 plan and would presumably lower taxes in inner cities. But how fair is that to people living elsewhere? And aren’t we back to more complexity?