Wisconsin Republican Sen. Ron JohnsonRon JohnsonTrump signs executive order creating new VA office Trump tax plan prompts GOP fears about deficit Lawmakers targeted as district politics shift MORE on Tuesday came out against the campaign tactics used by his state's Republican governor, Scott Walker.

Walker is running for reelection this year against Democrat Mary Burke, a former executive at Trek Bicycle Corp., a company her family founded. The company makes 99 percent of its bicycles overseas, a practice Walker's campaign has seized on in an ad against Burke. 

Walker's campaign also calls Burke "Millionaire Mary."

Johnson said he "would prefer they not" use that nickname when asked in an interview with the Milwaukee Journal Sentinel.

"Far too often in the political realm we demonize success, we demagogue against it," he said. "What we should be doing is incentivizing success."

On outsourcing, he added: "I don't want to demonize or demagogue against" the practice.

Walker is a potential 2016 presidential candidate, but first he has to get through a tough reelection race. A Marquette University Law School poll last month gave the incumbent just a 1-point lead. 

Johnson said "there are far better areas to address" than wealth and outsourcing.

"From my standpoint, we ought to be talking about ... how do you make Wisconsin a more attractive place for risk taking, business investment, business expansion?" he said.