Sen. Sherrod Brown (D-Ohio), who's a top GOP target in 2012, slammed Republican attempts to repeal the healthcare law. 

Speaking to voters at a senior center in Ohio Tuesday, Brown said the looming vote in the House for a full repeal of healthcare is "a colossal waste of time" and that the GOP is "just playing politics."

He told the crowd that no matter what happens in the House when members vote on repeal next week, it won't even get to the Senate floor with Democrats in charge of the upper chamber. 

A recent poll from Democratic-leaning Public Policy firm showed Brown vulnerable, with his approval rating below 40 percent among Ohio voters. The first-term Democrat's support doesn't reach higher than 43 percent in hypothetical match-ups with potential GOP challengers.

Republicans kept the state's other Senate seat in 2010, with Rob Portman (R) replacing retiring Sen. George Voinvich (R-Ohio). The GOP also won the state's governorship.

Despite Brown's perceived vulnerability, though, no Republican has jumped in the race against him -- yet.

Rep. Jim Jordan (R-Ohio), whose name is near the top of the list of potential challengers among Republican strategists in the state, said last month he is leaning against a run.

Former GOP Sen. Mike DeWine, who is Ohio's newly elected attorney general, also recently ruled out a Senate bid. Other potential GOP candidates include Secretary of State Jon Husted or Lt. Gov. Mary Taylor.