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In a sign that the scrutiny into his past is picking up alongside his  rising popularity, Newt Gingrich faced some of the toughest questions of his candidacy yet on Glenn Beck's radio show today.

The former House speaker this morning was grilled on a variety of past statements, from his support of the individual mandate to Medicare and climate change. And his remarks today are already coming under attack by opponents as being too liberal.

Gingrich today said he supports a "variation" on the individual mandate and that he would "implement" but not "impose" a controversial plan by Rep. Paul Ryan to overhaul Medicare.

Even though he has railed against the Democrats' health care law, the backbone of which is the individual mandate, Gingrich himself once supported it. He advocated imposing a requirement on Americans making more than $50,000 to have health insurance, and a voucher system that would give individuals a subsidy to have insurance.

"We ought to have some requirement to either have health insurance or you post a bond or in some way you indicate you are going to be held accountable," Gingrich said earlier this year.

"That is the individual mandate, is it not?" Beck, the conservative radio host, questioned today.

"It's a variation on it," Gingrich replied.

Gingrich also stood by his criticism of Ryan's controversial plan to overhaul Medicare, but he said he would "implement" it anyway, without imposing it.

Ryan's plan would revamp Medicare so that beneficiaries receive a set sum based on their income instead of the federal government paying for every service.

"Ironically, I would implement the Medicare reforms that Paul Ryan wants. I would implement them next year as an optional choice and I would allow people to have the option to choose premium support and then have freedom to negotiate with their doctor or their hospital in a way that would increase their ability to manage costs without being involved," he said. "But I wouldn't impose it on everybody across the board. I think that's a very large-scale experiment."

In another irony, on the day that President Obama is borrowing a page from President Teddy Roosevelt's playbook, Gingrich was pressed on his own comparison to the progressive president. In 2003, Gingrich declared that he was a "Theodore Roosevelt Republican" who believed there should be some "regulatory leaning" in the health sector.

Gingrich repeated those words again in a 2009 interview with ABC News, saying that the government needs to play a role in setting "the rules but not to run the system."

Gingrich defended his comments today, praising Roosevelt's progressive stance, saying he believes the federal government needs to impose "minimum regulatory standards of public health and safety" but he's against the "government trying to pick winners and losers."

"But you have selected a winner when you are for, quite strongly, the ethanol subsidies," Beck countered.

Gingrich replied that he only supports subsidies that would make the United States more energy independent.

But when questioned about subsidies contributing to out-of-control spending, Gingrich responded: "Well, it depends on what you're subsidizing."

"What I object to is subsidizing things that don't work and things that aren't creating a better future," he continued. "And the problem with the modern welfare state is it actually encourages people to the wrong behaviors, encourages them not to work, encourages them not to study."

Beck also confronted Gingrich on supporting the Medicare drug program for seniors. Gingrich has advocated federal aid for drugs for Medicare beneficiaries, and defended his stance when questioned why he backs such a big government plan while saying he wants to make government smaller.

"I don't see how one defends not having the ability to avoid the requirement for surgery, which is what this is all about," he responded. "And the question is can you live longer and more independently and more healthily with the drug benefit than without it. … The question in the short run is, so you want to have a system that basically leaves people with bad outcomes, or do you want to, in fact, maximize how long they can live and how independently they can live."

Gingrich also backtracked on his comments on global warming and the ad he made with Rep. Nancy Pelosi in the late 1990s calling for action on climate change.

"Well, I never believed in Al Gore's fantasies, and, in fact, if you look at the record, the day that Al Gore testified at the Energy and Commerce Committee in favor of cap and trade, I was the next witness and I testified against cap and trade," he said, even though his ad with Pelosi was for Gore's environmental group.

Rep. Michele Bachmann became the first shot at Gingrich, calling him a "frugal socialist" in an interview with Beck.

"I'm saying a frugal socialist, yes, because you're looking at proposals and programs that are, in effect, redistribution of wealth and socialism-based, and are we gonna have real change in the country, or are we going to have frugal socialist?" she said.