Mitt Romney is trying to move the debate over health care from the past (the program he enacted as Massachusetts governor) to the future (developing a Republican alternative to President Obama’s law).

But Romney’s principal problem with primary voters isn’t that Republicans don’t like his ideas, it’s that they just aren’t that interested in the subject.

Romney is trying to tackle his health policy problem head on with a Thursday speech in his native Michigan. He will lay out a four-point plan aimed at encouraging free-market solutions after repealing Obama’s law.

The general assumption in the pundit class is that Romney’s great political vulnerability is the provision in his 2006 law that, like Obama’s law, requires individuals buy private health insurance or be enrolled in a government program.

An individual mandate is certainly out of step with the libertarian fervor that has swept through the GOP in recent years. When Romney embraced the provision five years ago, it was considered the most Republican part of the law because it was all about personal responsibility. Remember that as a candidate, Obama attacked Hillary Clinton for backing such a mandate because he said it was too harsh.

Obama’s mandate flip flop has no doubt caused serious headaches for Romney. But the real problem for primary voters is that Romney did anything at all. Unless Republicans are fighting a Democratic health care initiative, they mostly don’t think about the issue as something for the federal government to be addressing.

While interest surveys of Republican voters in 2010 showed high levels of engagement on health care, it was negative in nature. GOP candidates were running on a platform of repealing Obama’s law, not enacting any particular policy of their own.

More telling are surveys from the 2000 and 2004 elections which occurred after the Republican anxiety over the 1995 Clinton health care plan and before the 2009-2010 Obama imbroglio. FOX News exit polls showed the issue of health care was all but irrelevant to voters who delivered two victories for George W. Bush.

In 2000, health care was seventh out of seven among the issues that mattered most to Bush voters at just 5 percent. Taxes (23 percent) and jobs and the economy (14 percent) mattered most.

In Bush’s 2004 win, the top decision drivers were moral issues (35 percent) and terrorism (32 percent). Health care came in with a scant 4 percent, ahead of only education, another subject many Republicans think isn’t a federal issue.

By comparison, Democratic voters show considerable, sustained interest. Those voters who supported John Kerry ranked health care third as a driving issue, ahead of moral values, terrorism, education and taxes.

A recent Onion headline kind of sums it up: “Mitt Romney Haunted By Past Of Trying To Help Uninsured Sick People.” That’s a punch line if you believe that health insurance is a proper job for the government, but not if you believe the government shouldn’t be involved.

It is precisely for that reason that congressional Republicans have struggled to produce an alternative plan with which to replace Obama’s law. Health care is not something that their party has put much thought into. Democrats struggle on military issues and deficits for the same reason – policy development follows political interest.

Working in Romney’s favor is the fact that with Obama’s law in place, Republicans have taken a more serious look at the issue. The accepted wisdom among party leaders is now that some alternative must now be offered, particularly since so much of the exploding federal debt can be attributed to existing federal health care programs.

Republicans can’t politically afford to repeal the president’s plan without offering anxious independent voters an alternative and neither can they balance the budget without taking on Medicare and Medicaid. This works in Romney’s favor since he is the only contender with practical experience on the issue.

It will only work, though, if he can force the other 2012 Republican contenders to lay out plans of their own. That’s why Romney is delving into specifics now. He not only wants to move the discussion away from whether mandates are good or bad, but to also force everyone else to address the controversial topic with an answer beyond “repeal Barack Obama’s job-killing health care plan…”

But, given the low levels of interest in health policy among the Republican faithful, Romney’s foes will likely suffer little political consequence for staying vague on the subject.

In 2008, Romney tried to allay voter concerns about his Mormon faith with a major policy speech on religion in America. The speech was good, but the problem he had then is likely to be the same one he will have now: Romney had to highlight a liability while his opponents could benefit by saying nothing at all.

John McCain didn’t feel moved to explain his Episcopalianism and Tim Pawlenty won’t feel obliged to start defining and defending his ideas for a national health plan.

Chris Stirewalt is FOX News’ digital politics editor. His political note, Power Play, is available every weekday morning at FOXNEWS.COM.