Click here to watch "Ethanol."

The mudslinging continues between Missouri gubernatorial hopefuls Rep. Kenny Hulshof (R) and state Treasurer Sarah Steelman (R) in a pair of new ads.

Steelman's "Ethanol" (subscription), released Monday, underscores the candidate's changed position on the state's ethanol mandate, enacted in January, which requires stations to sell fuel with 10 percent ethanol as long as it isn't more expensive than regular gasoline. Earlier this year, she tentatively supported the law, but now says she believes ethanol, which is derived from corn, is part of the cause for high food and gasoline prices. In the ad, an announcer takes a jab at Hulshof for supporting the mandate, quoting him as saying, "The idea of high corn prices is appealing to me."

Hulshof's latest ad (subscription), launched Thursday, opens with a splatter of mud, as an announcer says, "Sarah spends all her time attacking Kenny Hulshof. She won't talk about her own record." He then compares Steelman to state Attorney General Jay Nixon, who is running for governor on the Democratic side.

"She was the only Republican to side with trial lawyers on frivolous lawsuits, the same trial lawyers who bankroll Sarah Steelman's campaign," he says. "Now, who does that remind you of? Sarah Steelman -- nasty attacks, bad ideas -- just like Jay Nixon."

"The Steelman campaign plan begins and ends with negative attacks," Hulshof spokesman Scott Baker said. "This ad simply points this out." He added that more similarities can be drawn between Steelman and Nixon than just the ones the ad cites: Both their strategies implement an "all-attack all-the-time mode of campaigning," he said. "It's a very natural comparison."

Baker said it was "curious" that Steelman chose to highlight her rejection of the ethanol mandate in her latest ad. "This is a farm state that not only benefits from the production of ethanol, but studies show that ethanol improves gas prices here, or at least eases the pain here," Baker said.

The intense fight seems to have benefited the Democrats; Nixon, who is running unopposed in the primary and has yet to release an ad, leads both Republicans in new St. Louis Post-Dispatch/KMOV-TV polling by nearly 20 percentage points.