President Obama will be in Kansas City on Thursday to stump for Robin Carnahan, Missouri’s leading Democratic Senate candidate. On the other side of the aisle, Rep. Roy Blunt is facing off against Chuck Purgason, a state senator, in Missouri’s GOP Senate primary. Here’s Blunt’s new ad, where the seven-term congressman touts his dairy-farm roots and his classroom cred:

According to National Journal, Purgason has “ambushed Blunt over his long career in D.C., courted the Tea Party, and launched radio ads comparing himself to Sharron Angle. . . Public polls have shown Blunt is well ahead of Purgason. But the new Blunt ad signals his nervousness, and the possibility that Blunt won’t be the runaway winner he wants to be.”

A Rasmussen poll released last week shows Blunt with a five-point lead over Carnahan, 48 percent to 43 percent, with six percent undecided. Purgason was recently endorsed by Joe the Plumber. Sarah Palin has donated $2,500 to Blunt. Karl Rove is another prominent Blunt backer. The primary is on August 3.