Survey USA recently released new polling numbers for Iowa, and it wasn’t good news for Governor Chet Culver. Senator Chuck Grassley’s approval was at a multi-year low in the same poll.

Links, numbers and some analysis are after the jump.

SUSA found Culver’s approval rating at 42 percent, with 50 disapproving. In February and March, SUSA found that 46 percent of Iowans approved of Culver’s performance as governor.

If you look at the graph of SUSA’s numbers for Culver since he took office, you’ll see that 42 percent is the lowest approval number SUSA has ever recorded for him. For most of his tenure, his approval has been in the 50s. He dipped into “net negative territory” (with disapproval exceeding approval) from February through April 2008, then bounced back above 50 percent for the rest of last year. When I first saw the graph, I thought maybe Culver got a bump during last summer’s floods, but his approval rating was already noticeably higher in May 2008.

The trendlines for Culver got me wondering whether the governor’s difficult working relationship with Democrats in the Iowa House and Senate is at the heart of his poor numbers in February through April of 2008 and 2009. The most recent poll was in the field on April 24 through 26, which coincided with the final marathon days of the 2009 legislative session.

If a “legislature effect” is dragging Culver’s numbers down, add that to the list of reasons the governor and statehouse leaders need to figure out a way to cooperate more effectively during the 2010 session.

Of course, we’re also in the middle of an economic recession, which has been the focus of massive media coverage since the start of the year. In the coming months, Culver’s I-JOBS program will lead to lots of new spending on infrastructure projects. It will be interesting to see whether his approval goes up.

It’s also possible that Culver’s approval slipped a little in April because of the Iowa Supreme Court’s ruling in Varnum v. Brien. The Republican Party of Iowa trumpeted this poll as a sign the public disagrees with Culver on labor unions, taxes, spending and gay marriage.

It’s worth noting that SUSA’s numbers on Culver run a bit low compared to other pollsters. For instance, in late March SUSA had Culver at 46 percent approval while Selzer and Associates put that figure at 55 percent, and the Republican firm Hill Research measured his approval at 52 percent. Nevertheless, the SUSA numbers and trendlines bear watching. If other polls also put Culver’s approval in the low 40s, I would tend to agree with Bleeding Heartland user American007 that he looks vulnerable (with the caveat that the GOP would have to nominate someone other than Bob Vander Plaats or Steve King).

Grassley’s latest approval number, according to SUSA, is 59 percent, with 32 percent disapproving. That’s well out of the danger zone for an incumbent, but low for Grassley, who was at 71, 71 and 68 in SUSA’s polls for January through March. In fact, SUSA has only found Grassley’s approval below 60 once in the past four years of polling.

My hunch is that Grassley’s support among Republicans has dropped because he hasn’t been pounding the table about overturning the Iowa Supreme Court ruling on same-sex marriage. It’s also possible that his approval rating fell for some other reason, or that this poll is an outlier.

Whatever the reason, it’s interesting that both Grassley and Culver hit multi-year lows in the same SUSA poll. Senator Tom Harkin’s approval in the poll was 51 percent, with 38 percent disapproving. That’s only slightly down from SUSA’s March poll that put Harkin’s approval rating at 53 percent.

Incidentally, SUSA’s April survey found that 59 percent of Iowans approve of the job Barack Obama is doing, down about ten points since the beginning of the year. There was no statistically significant gender gap; Obama’s approval was 59 percent among men and 60 percent among women. The numbers for Culver showed a clear gender gap, with 47 percent approval among women and only 37 percent approval among men.

Offer your own theories about any of these poll numbers in this thread.