Via Todd Dorman’s blog, I see news that will make thegolddome happy: someone has done a public poll on the Iowa GOP gubernatorial primary. Public Policy Polling found former Governor Terry Branstad leading Bob Vander Plaats 46 percent to 31 percent, with State Representative Rod Roberts well behind at 13 percent. The firm surveyed 474 “likely GOP primary voters” between May 25 and 27, and the margin of error is plus or minus 4.5 percent. The polling memo by Tom Jensen notes, “Branstad gets 42-68% of the vote across the ideological spectrum, but does worst against the 74% conservative majority, edging Tea Party favorite Vander Plaats by just 41-35.”

This poll supports what I’ve been thinking for months about Roberts. He is the best surrogate Branstad could have in this primary, diluting the votes of the social conservative base that doesn’t trust the former governor. If one candidate consolidated the “not Branstad” vote, the topline result would be nearly a dead heat.

If PPP’s survey is accurate, Branstad will win next Tuesday’s primary, but with the advantages he took into this race he should be getting 60 to 70 percent of the Republican vote. He’s done the job before, he will have spent more than $2 million before the primary (more than his opponents combined), and he has been advertising statewide on television and radio since the beginning of April. Roberts and Vander Plaats could manage only limited ad buys, and Vander Plaats just went up on television the day before PPP’s poll was in the field.

Incredibly, this is the first public poll of the Republican primary since last July, when The Iowa Republican blog commissioned a survey by Voter/Consumer research. That poll found Vander Plaats way ahead of the rest of the declared Republican candidates, with only Branstad hypothetically able to make the primary competitive.

Branstad created an exploratory committee to run for governor last October. Since then, Selzer has done two Iowa polls for the Des Moines Register, Research 2000 has done three polls for KCCI-TV, The Iowa Republican commissioned another poll in January, not to mention several Iowa polls by Rasmussen. All of those surveys tested Governor Chet Culver against his Republican challengers but not the Republican primary. The lack of polling on Branstad against Vander Plaats and Roberts is a continuing mystery to me. I read Swing State Project regularly and have seen dozens of polls of Democratic or Republican primaries in other states. You would think that at the very least The Iowa Republican blog would want to poll the GOP primary. The fact that they haven’t suggests that last summer’s primary poll may have been intended primarily to help the people recruiting Branstad to run for governor again. Rasmussen is the most prolific pollster in the country, and has polled Republican primaries in many other states. Maybe Rasmussen really is just interested in setting a narrative rather than polling the most newsworthy races.

PPP also polled the Democratic primary for U.S. Senate and found Roxanne Conlin way ahead with 48 percent, compared to 13 percent for Bob Krause and 8 percent for Tom Fiegen.

Share any relevant thoughts in this thread.

UPDATE: Kathie Obradovich highlighted something worth noting from PPP’s polling memo:

Among voters that actually know who Vander Plaats is- whether they see him favorably or unfavorably- he leads Branstad 42-37. The question is if there’s enough time left for Vander Plaats to completely make up the huge gap in name recognition he began the campaign with.

Vander Plaats was never going to be able to match Branstad’s spending dollar for dollar with the huge support for Branstad among Iowa’s business Republican elite. But if Vander Plaats had saved more of what he raised in 2009, he might have been able to raise his name recognition much more this spring.

SECOND UPDATE: Iowa Independent highlighted another part of the polling memo:

There are very clear age divisions in the race. It’s tied among voters under 45, who may not even remember Branstad’s time as Governor. But he’s up 55-20 with senior citizens, who are certainly likely to remember his tenure, and that’s fueling most of his overall victory.

I would think almost anyone over 30 remembers Branstad as governor. I suspect that this discrepancy tells us there are a lot more moderate Republicans over age 45 than under age 45. Branstad leads Vander Plaats among moderates by a huge margin in the poll. The Republican Party has grown much more conservative in the last decade or two, so younger moderates might naturally identify more with Democrats or no-party voters.