Rep. Roy Blunt (R-Mo.) has built a lead over Secretary of State Robin Carnahan (D) in Missouri's Senate race.

The first numbers released after the healthcare bill was signed into law show Blunt opening up a 45-41 lead. The same firm who conducted the poll, Democratic-leaning Public Policy Polling, had Carnahan up 43-42 in November.

Much of Blunt's lead appears to be a symptom of President Obama's approval in the state. More than half -- 52 percent -- of voters disapprove of Obama, while 43 percent approve. Blunt also leads among independents, 47-35.

But Carnahan maintains superior favorability numbers, at 38 percent positive and 43 percent negative. With Blunt, those numbers are not great -- 25 percent and 41 percent, respectively.

Unlike other races, the Missouri Senate race hasn't see a great deal in the way of public polling.