For Missouri voters, the No. 1 issue has consistently been Iraq. A Mason-Dixon poll showed that roughly a quarter of voters said it was the most important issue this election cycle. McCaskill has consistently called for U.S. troops to be redeployed to other areas in the Middle East within the next couple of years. Talent, in a televised debate on Meet the Press, chided McCaskill for what he characterized as "cut and run" policies. He said even if he had known everything he knows today, he would still have voted for the war in Iraq.

Analysts have insisted that the closeness of the race— it's been virtually tied in most polls since September—indicates the sway that so-called "values voters" still hold in Missouri. One fifth of Missouri's voters say issues like gay marriage and abortion will be the top factor determining their Senate vote. Even though McCaskill has made courting rural voters a key focus of her campaign—she has crisscrossed the southern section of the state dozens of times in her blue campaign RV—recent polls still show that 57 percent of southwestern Missouri voters still plan to vote for Talent, while only 33 percent favor McCaskill. Roughly 8 percent of those voters remain undecided.

Rallying over the weekend highlighted the strategy of both campaigns. McCaskill has tried to repeatedly to tie Talent to President Bush, who holds an approval rating in the Show Me State in the low 40s. She spoke at a slate of mostly African-American churches on Sunday with Barack Obama, the popular Illinois senator who has appeared three times in the state on her behalf. McCaskill emphasized that Talent has voted 94 percent of the time with Bush in his four years in the Senate.

On Sunday, Talent hit up the Southeastern portion of the state, where he spoke to 50 energetic supporters at a rally in Cape Girardeau. His loudest applause lines came when he emphasized his opposition to gay marriage and abortion.

Both parties have pumped millions into turnout efforts, and over the weekend Talent campaign manager Lloyd Smith said he expected 10,000 volunteers to help. McCaskill had strong words for her supporters on recent coverage of Missouri's Get Out the Vote effort; she agreed to run for the Senate seat after securing promises from national Democrats that they would pump millions into upgrading Missouri's voter lists.

"If I read one more time about the vaunted GOP turnout machine, I'm going to get nauseous," McCaskill said. "Do you think Missourians are more motivated to stay exactly the way we are now, or do you think they are motivated for change?"

Amendment 2, a Missouri ballot initiative favored by McCaskill and opposed by Talent, would encourage additional stem cell research. Although the majority of Missourians support the measure, recent advertisements that feature St. Louis Rams quarterback Kurt Warner and St. Louis Cardinals pitcher Jeff Suppan challenging the proposal, may be partially responsible for increasing the number of undecided voters on the issue fivefold since June. Some analysts argue church efforts to turn out anti-stem-cell voters may hurt McCaskill.

—Angie C. Marek