It would be hard to argue that Mike Huckabee's decision not to run for president is good news for Republicans on the ballot in Missouri 2012. As you can see the most recent PPP Polling survey, conducted April 28 to May 1, Huckabee was the strongest challenger to Barack Obama in the state. Obama trailed Huckabee and Romney in their poll, and we haven't even begun to see a real discussion of Romney's previous support for a federal health insurance mandate.
From PPP's blog post on the most recent presidential numbers in the Show-Me State.
As such, he trails Mike Huckabee, 44-49, and Mitt Romney, 43-45--mirrors of his 43-49 and 43-44 deficits two months ago. Obama leads Newt Gingrich, 46-44; the two were tied at 44% previously. He also matches his lead over Sarah Palin, 48-43, and bests Donald Trump, tested for the first time, 46-41. Obama is still losing double-digit percentages of Democrats, as against McCain, but he at least narrowly leads with independents, whom McCain barely won in 2008.
Despite his unpopularity, the president is seen in a better light than all the Republicans but Huckabee. Huckabee stands at 43-38, Romney at 31-45, Gingrich 29-50, Palin 33-56, and Trump 24-65.