"I have been all across this beautiful land and I have seen how the big corporations are squeezing out our family farms," Nelson said in a cramped news conference aboard his tour bus with the Democratic candidate. "I know she'll do what's right to protect this long-standing way of life."

It's just the latest turn of the wheel in a campaign that's focused heavily on wooing rural voters, a key constituency in the Republican stable. McCaskill, who hails originally from the same small town in southern Missouri as Republican Sen. Kit Bond, often travels to far-flung rural corners of the state in a giant blue campaign RV. She also frequently emphasizes on the stump that she has the support of the National Farmers Union, a group of roughly 250,000 family farmers and ranchers, which McCaskill says reflects "the little guys."

Talent has made boosting ethanol usage a touchstone of his campaign. He frequently cites his move this year to include a provision in the energy bill that will add 7.5 billion gallons of ethanol, biodiesel, and other renewables to the country's fuel supply by 2012. His campaign frequently touts an endorsement by the Missouri Farm Bureau, which represents 104,000 farmers and ranchers in every county in the state. Talent is also a member of the Senate Agriculture Committee.

McCaskill has portrayed Talent as a friend of corporate agriculture, and his campaign took little time this week to begin attacking the Nelson endorsement. Rich Chrismer, a Talent spokesman, said the National Biodiesel Board, which boasts Nelson as a member, was behind the senator's ethanol legislation.

"We are content to put our endorsements by the Missouri Farm Bureau, the Missouri Corn Growers Association, and the Missouri Soybean Association up against anyone's endorsements," Chrismer added.