Iowa Republican caucus-goers have switched their allegiance from one joke candidate selling books to another. Former House Speaker Newt Gingrich leads the field in the latest poll by Selzer and Co for the Des Moines Register. Meanwhile, former Massachusetts Governor Mitt Romney trails the latest “not Romney” contender by a larger margin than in the Register’s other polls this year.

The Des Moines Register released the toplines from the poll last night, adding more details Sunday morning. Selzer and Co surveyed 401 “likely Republican caucusgoers” between November 27 and 30, and 25 percent of respondents said Gingrich would be their first choice if the caucuses were held today. Representative Ron Paul was in second place with 18 percent, and Romney dropped to 16 percent. The poll’s statistical margin of error is plus or minus 4.9 percent.

The rest of the field was far back, with former Godfather’s Pizza CEO Herman Cain and Representative Michele Bachmann tied at 8 percent, Texas Governor Rick Perry and former U.S. Senator Rick Santorum tied at 6 percent, and former Utah Governor Jon Huntsman at 2 percent.

Cain and Gingrich in effect switched places since the Register’s last Iowa poll in October. That survey found Cain leading with 23 percent, with Gingrich tied for fifth at 7 percent. Selzer and Co conducted an Iowa poll for Bloomberg in November and found Cain, Paul, Romney and Gingrich bunched together at the top.

Cain held a press conference on Saturday to announce that he is suspending his presidential campaign. The Des Moines Register may have helped that decision along with a front-page story on Friday highlighting Cain’s decline to 8 percent in the latest poll. (That story did not reveal the new levels of support for the other candidates.) I still believe Cain’s candidacy was mostly about selling copies of his memoirs. His travel schedule this year has made more sense as book tour marketing than as early state organizing. The same could be said for Gingrich.

I was skeptical about a recent Newsmax/InsiderAdvantage survey showing Gingrich way ahead in Iowa with 28 percent, followed by Paul (13 percent) and Romney (12 percent), but those numbers are not far from the Register’s findings.

Even more encouraging for Gingrich, the Register’s poll found him leading as a second-choice candidate too. Some 18 percent of respondents named Gingrich as their current second choice, followed by Romney (15 percent), Perry (12 percent), Bachmann (11 percent), not sure (10 percent), Cain (9 percent), Paul (7 percent), Santorum (4 percent) and Huntsman (2 percent).

How depressed would you be to be Santorum right now? He’s put in a real effort in Iowa, but the roulette wheel has landed on just about every “not Romney” but him. Maybe he will pick up some of Cain’s former supporters.

The seven major Republican presidential candidates will debate twice in Iowa during the next two weeks. Gingrich has been a crowd-pleaser in most of the debates so far, and perhaps he will solidify his lead during the final stretch. On the other hand, debates create an opening for other candidates to hammer Gingrich’s stand on immigration and unflattering aspects of his political background. I’m not talking about his three marriages, I mean his former support for government action to combat climate change, his -unregistered lobbying- “consulting” for Freddie Mac and other groups.

Santorum and Bachmann have been solid in the GOP debates I’ve watched so far. I feel they have more potential to gain in the final weeks than Ron Paul, because Paul’s foreign policy views disqualify him from serious consideration for most Republicans. Perry is now spending more money on Iowa television advertising than anyone else, but he would need to have his best debates ever to bounce into contention here.

Romney is in a dangerous place. For most of the year, he seemed to have solid support here in the low 20s, which probably would have been good enough for second place in the caucuses. Not bad for a guy who made virtually no effort here. Now several polls have found him slipping to the low to mid teens. Romney recently added staff in Iowa and started running this television commercial here on December 1. He generally does well in debates too. Will he be able to stop the bleeding? Romney has a path to the nomination even if he is embarrassed by the results on caucus night, but Gingrich is gaining on him in New Hampshire. With his various mansions, Romney isn’t in position to criticize Gingrich for his taste in luxury jewelry.

Republican insiders are horrified by the thought of Gingrich as the GOP presidential nominee. This story by Taylor West and Peter Bell includes many amusing comments:

“Winning the presidency is all about discipline, focus, and organization,” said one Republican Insider, “none of which are strong suits for Gingrich.”

“With Newt, we go to bed every night thinking that tomorrow might be the day he implodes,” said another Republican. “Not good for our confidence – or fundraising.” A third Republican stated plainly, “Gingrich is not stable enough emotionally to be the nominee – let alone, the president.” […]

“Bigfoot dressed as a circus clown would have a better chance of beating President Obama than Newt Gingrich, a similarly farcical character,” quipped a Republican.

“Come on,” sighed another GOP Insider, “the White House is probably giving money to Gingrich as we speak.”

Underlining the mixed-up nature of this field, several Christian conservatives have decided not to endorse any candidate before the caucuses. Iowa Republican National Committeeman Steve Scheffler said this week that neither he nor the Iowa Faith and Freedom Coalition, which he leads, will publicly support a candidate before January 3.

Bob Vander Plaats has yet to announce which way the FAMiLY Leader will go. The group is considering four candidates: Bachmann, Perry, Gingrich and Santorum. An anonymous group calling itself “Iowans for Christian Leaders in Government” recently warned Vander Plaats not to endorse Gingrich. I think it would be hilarious for Iowa’s leading self-styled “marriage defender” support that creep.

Bachmann’s campaign probably didn’t help its cause by using the Network of Iowa Christian Home Educators’ mailing list without that group’s permission.

Any comments about the Republican presidential field are welcome in this thread.

UPDATE: The Sioux City Journal endorsed Romney on Sunday:

In our endorsement of Mitt Romney before the Iowa Caucuses four years ago, we wrote of America’s need for a president possessed of “energy, intellect, vision, charisma and experience” to lead the nation in meeting “formidable, complex, divisive, political and dangerous” challenges.

Since then, the nation’s challenges – in particular, its domestic economic challenges – have grown still more acute.

Within this year’s Republican presidential field, Romney again stands out as the candidate who is best prepared through experience, skills and qualities to lead the country. Today the Journal endorses the businessman, former Massachusetts governor and former Winter Olympics CEO in the Jan. 3 caucuses.

NBC News/Marist released a new Iowa survey on December 4; click here for full results (pdf). Here were the first-choice results among the sub-sample of voters likely to participate in the GOP caucuses:

Gingrich 25 percent

Romney 18 percent

Paul 16 percent

undecided 11 percent

Perry and Cain 9 percent each

Bachmann 5 percent

Santorum 4 percent

Huntsman 2 percent

Second choices:

Romney 19 percent

Gingrich 18 percent

Perry 13 percent

Bachmann 12 percent

Paul 11 percent

Cain 10 percent

undecided 8 percent

Santorum 7 percent

Huntsman 3 percent

Mark Murray of NBC summarizes some other findings from this survey:

A combined 71 percent of likely Republican caucus-goers in Iowa, as well as a combined 71 percent of likely GOP primary voters in New Hampshire, view Romney as either “moderate” or “liberal.”

Among Iowa Republicans identifying with the Tea Party — who make up about half of all likely caucus-goers — Gingrich leads Romney, 32 percent to 11 percent. And among Tea Party Republicans in New Hampshire, Gingrich and Romney are tied at 33 percent each.

What’s more, 63 percent of likely Iowa caucus-goers and 60 percent of likely New Hampshire primary voters say it’s unacceptable if a presidential candidate supports an individual health-care mandate (as Romney helped enact in Massachusetts).

By comparison, 47 percent of likely Iowa caucus-goers and 41 percent of likely New Hampshire primary voters say it’s unacceptable if a candidate favors some sort of limited legalization — or “amnesty” — for illegal immigrants living in the United States (as Gingrich has suggested he supports).

Measuring Obama

Turning to the general election in Iowa and New Hampshire, President Barack Obama’s approval rating remains underwater in both states.

Forty-three percent of registered voters in Iowa approve of his job performance, which is up one point from October. In New Hampshire, 40 percent of registered voters approve of his job performance, up two points.

Yet — with one exception — he leads all GOP challengers in hypothetical match-ups in the Hawkeye State. He’s ahead of Romney by seven points among registered voters (46 percent to 39 percent), Gingrich by 10 points (47 percent to 37 percent) and Perry by 11 points (48 percent to 37 percent).

The one exception: Paul ties him at 42 percent for each.