ABCNEWS.com

Although republican presidential hopeful Mitt Romney has been criticized by fellow republicans for the controversial health care law he enacted as Governor of Massachusetts, one senior U.S. Senator has some unorthodox advice for him: “stick to your guns.”

Senator Lamar Alexander, R-Tenn., tells ABC News he thinks Romney should not only vigorously defend the health care law he signed as governor, but also resist the recommendations from fellow republican heavy hitters like Tea Party kingmaker Senator Jim DeMint, R-S.C., to admit he made a mistake.

“I wouldn’t do it,” Alexander said during an interview on ABC News’ Subway Series with Jonathan Karl . “I would think less of him if he did that.”

You can watch more of ABC’s Subway Series with Jonathan Karl HERE .

Alexander also praised the other presumed republican front-runner, Texas Governor Rick Perry, for defending one of his major political liabilities.  Alexander says Perry, who has come under fire recently for defending legislation he signed into law as Governor that grants in-state tuition rates and financial aid to the children of illegal immigrants, is acting “presidential.”

“He has a view that most republican primary voters don’t agree with and he stuck to his guns. I admired that,” Alexander told ABC News.

When asked if Governor Perry’s comments that social security is a “ponzi scheme” or “monstrous lie” are palatable to voters in a general election, Alexander suggested Perry had room to grow as a presidential candidate.

“There’s a big difference between being governor and being president, even if you’re from a big state,” Alexander said.  “Going from governor to presidential primaries is like going from eighth grade basketball to the NBA finals and you have to be careful. People expect something of a president.”

Even so, Alexander, who has run for president twice himself, says the most important factor in winning a presidential nomination which candidate “looks the most presidential” when the nomination is decided.

Earlier this week  Alexander resigned his position as Chairman of the Senate Republican Conference to focus more on helping building consensus within the deeply divided Senate “so that it can deal better with serious issues.”

Alexander says he’s optimistic about Congress’s ability to tackle at least one of those serious issues: the deficit.  He tells ABC News he’s confident in so-called “Super Committee’s” ability to reach consensus on where and how to shave $1.5 trillion from the federal budget.

“I think the most encouraging thing in the Senate is that you now have 37 or 38 senators equally divided between the parties who are united behind the principals of the old ‘Gang of Six’ and saying to the Super Committee, go big, go as big as you can,” Alexander said.

When asked about the differences between republicans and democrats on taxes and government health care benefits, Alexander said he was confident those divisions would be ironed out.

“We’re going to try,” Alexander said on reconciling the differences between the parties.  ”I mean what we do is do the best we can.”