Walker, who survived a highly partisan recall battle last week, said on CBS' "Face the Nation" Sunday that Romney would have to offer voters more than just replacement for the current president.
"Gov. Romney has a shot if the 'R' doesn't stand for Republican, but reformer," Walker said, adding "I don't think we win if it's just about a referendum on Barack Obama."
Voters in Wisconsin's recall election appeared to respond to the idea of a governor willing to make tough decisions and pundits predicted they would lean to Romney, the presumptive GOP nominee, if he took a similar stance. Obama held a 7 percentage point lead in the state in recent polls.
Walker did not, however, embrace Romney's recent statement tying the Wisconsin recall to an anti-government sentiment among the voters. Walker said his efforts to reform the state workforce were aimed at saving jobs.
"I know in my state our reform allowed us to protect firefighters, police officers and teachers; that's not what I think when I think of big government," said Walker.
Walker added that the best answer to the nation's sluggish economy was getting the private sector back in gear rather than dramatically increasing the size of the federal government.