Wisconsin Gov. Scott Walker left the door wide open to a 2016 presidential run while warning the party not to choose a Washington lawmaker to be the nominee, considering Congress' record low approval ratings.

While he offered praise for several GOP colleagues on Capitol Hill; including Rep. Paul Ryan and Sens. Ted Cruz, Rand Paul and Marco Rubio; he said all are too closely associated with the Beltway to be the best nominee.

“I think it's got to be an outside,” he told ABC's Jonathan Karl on an episode of “This week” that aired Sunday. “I think both the presidential and the vice presidential nominee should either be a former or current governor, people who have done successful things in their states, who have taken on big reforms, who are ready to move America forward.”

Karl specifically asked Walker what he thought of Ryan, the 2012 vice presidential nominee, along with Cruz, Rubio and Paul.

“All good guys, but ... it's got to be somebody's who's viewed as being exceptionally removed from Washington,” he said, noting that he would be the president of Ryan's fan club if he had one.

When asked directly whether he would run himself, Walker said, “I don't rule anything out.”

The governor also tepidly criticized the strategy, led by Cruz, to shut down the government in order to try to delay or defund Obamacare.

“I think so,” he said when asked if it was a mistake.

The Wisconsin governor, who kicked up a storm of controversy in 2011 by pushing through a bill limiting the power of unions, also pointedly said state-level Republicans were showing they could lead and solve problems, while the GOP in Washington has displayed an unwillingness to compromise.

“Republicans at the state level are showing we're much more optimistic, we're speaking in terms that are much more relevant to where real voters are at,” he said.