Several Senate Democrats in red-leaning states are in a particularly tough spot, having to defend the health care law to an increasingly wary voters. Republicans have made bashing the law their main campaign strategy, believing that tactic is a winning strategy in 2014.
Manchin said President Obama should pause implementation of the law until 2015, saying failure to meet expectations could cause a "complete meltdown."
Manchin and Sen. Mark Kirk, R-Ill., have sponsored legislation to do that, arguing that the administration should give itself more time work out some of the program's specifics.
Still, Manchin was supportive of the health care law's general aim.
"Something's wrong [with health care in the United States]. We've got to do better. Is this the right thing? Probably not. Is it a step moving it? Yes. We're moving the ball forward," Manchin said.