Former Governor Terry Branstad maintains a 16-point lead over Governor Chet Culver, according to a new Rasmussen poll released today. The Republican pollster surveyed 500 “likely voters” in Iowa on March 17. Branstad led a match-up against Culver by 52 percent to 36 percent, similar to the 53-37 lead Branstad had in Rasmussen’s February poll. The latest poll has Bob Vander Plaats leading Culver 42-40, a slight change from the 46-40 lead Vander Plaats had in the February poll. Rasmussen found Culver leading Rod Roberts 40-38 (Roberts was not included in the February poll).

We’ve now seen several polls showing Branstad above the 50 percent mark against Culver. Clearly Culver needs to bring up his own support; Rasmussen’s survey put the governor at 41 percent approve/57 percent disapprove, and it’s never good for an incumbent to barely break 40 percent against all challengers.

Culver also needs Branstad’s numbers to come down. I have been expecting Branstad to get roughed up during the GOP primary, but I question whether Vander Plaats will have the resources to publicize his case against Branstad effectively. Roberts looks mostly like a threat to Vander Plaats from where I’m sitting, so I doubt he will make a strong case against Branstad. Chris Rants seemed determined to put Branstad’s record under scrutiny, but last month he quit the governor’s race after failing to raise enough money for a campaign.