Former presidential candidate Mitt Romney called on Republicans to "stand up" to President Obama and his policies on the economy, health care and energy, in a wide-ranging interview with FOX News. 

At a time when Republicans desperately are searching for a unifying leader and message, and Democrats add to their ranks in Congress, the former Massachusetts governor and 2008 presidential candidate took a no-excuses attitude toward his party. 

"I think Republicans have to stand up and make it very, very clear that we run the risk as a nation of having the entire world lose confidence in the currency of the United States and that would lead to something worse than a recession -- that would lead to an extraordinary slowdown globally that would hurt us more than any other," Romney told FOX News Tuesday evening. 

He said the GOP has a responsibility, however thin their numbers, to stand up to stimulus spending and excessive government intervention in health care. 

"When the stimulus bill is wrong, when it wastes money and threatens the viability of our currency long-term, you have to stand up and say 'no.' When a health care plan says we're going to have the government take over health care which is roughly a fifth of our economy, Republicans are going to have to say 'no' to that," he said. 

Romney was at the Massachusetts State House Tuesday night for the unveiling of his portrait as the 70th governor of the commonwealth. It was a reunion for Romney backers from his days in the capital as well as his campaign for president, which some say hasn't really ended. 

With the ranks of GOP rising stars thinning as a result of recent scandals and missteps, Romney is frequently talked about as a 2012 contender. Though not playing it up, Romney isn't ruling out another run at American politics' biggest prize. 

"At this stage it's too early to try to see what's going to happen down the road," he said. "I haven't closed the door on my future, but I'm not walking through it either." 

According to a recent Pew poll, among Republicans Alaska Gov. Sarah Palin -- despite the unceasing drama surrounding her and her family -- is the GOP's most popular leader, with a 73 percent approval rating. Romney had 57 percent. 

The former governor is lately enjoying a bump in the polls. His overall favorability rating in the Pew poll of 1,502 adults taken June 10-14 clocked in at 40 percent -- a 10-point increase since he conceded the 2008 GOP nomination to Sen. John McCain last year. 

Romney is also seeing a big turnaround among independents, according to the poll, whose margin of error was 3 percent. In February 2008, just 29 percent of independents had a positive impression of Romney while 46 percent had a negative view. That balance has since reversed, with 44 percent now viewing Romney favorably and 25 percent having a low opinion of him.

The wealthy businessman, whose public image during the campaign was regarded as almost too-perfect, is still held up as an example by his political peers. 

The former governor was introduced Tuesday by sitting Massachusetts Gov. Deval Patrick, a Democrat, who pointed to Romney's universal health care plan for the state as a possible model for a nationwide plan. 

On health care, Romney pointed to the successes of his own plan but criticized Obama's for its emphasis on a public option. 

"The president's plan makes an enormous error by saying we're going to put government into the insurance business. We got everyone in Massachusetts insured and we did it without putting government into the insurance business," he said. "We said instead we're going to help people get private free enterprise kind of insurance they can buy from a number of different companies." 

He said the system led to plunging premiums while offering a healthy choice of options for consumers. 

"It's working well. We got 440,000 more people insured than when the plan was put in place, it costs less than 2 percent of the state budget -- it's a plan that's working, it's a good model," he said. 

Romney also took issue with the climate change bill that passed the House of Representatives last week, saying it was corrupted by special interests. 

"It's a lobbyists' delight and as a result it's a lousy piece of legislation. It should not have been passed, it's going to cost the American consumers a lot of money, it's going to cost us a lot of jobs. Yeah we'll create jobs making windmills and solar panels and that's wonderful, but were going to lose a lot of other jobs ... that are creating products that use energy," he said. 

Romney repeated the refrain of cap-and-trade critics, saying the stringent measures in the bill would result in jobs going overseas so companies avoid the "high costs" stemming from the package. 

Romney said he thinks the GOP needs to keep reaching out to a broader range of voters, and that it would be "unfortunate" for the party to box itself in. 

"I think we have to make it very clear that our principles are right and that what we believe will create a stronger more prosperous America, and we have to make sure to communicate that more effectively to a broader audience than we have," he said.

FOX News' Carl Cameron and Jake Gibson contributed to this report.