According to the latest Wall Street Journal/NBC News poll, 55 percent of registered voters say the outcome of this election will make “a great deal of difference” in their lives. That’s a 10 percentage point increase over the 2004 election, and more than double the percentage of voters who felt that way about the elections of 1996 or 1992. The stakes this year are higher — and most voters know it.

That’s not always the case. In fact, any given presidential election is usually less consequential than the competing campaigns suggest. Candidates have every incentive to promise you the sun, moon and stars, and so they do. But no sooner does the winner adjust his chair in the Oval Office than the White House budget director tells him they can only afford the moon and a few stars. Then the moon gets taken out by a filibuster, and the rule-writing process makes it so hard to get a star that pretty much no one ever does. And that’s a good-case scenario. The Moon, Stars and Sun Act may never even make it out of the House Ways and Means Committee.

This year isn’t like that. The most important fact of the 2012 election is that the Affordable Care Act was passed in 2010; it just hasn’t been fully implemented yet. If President Barack Obama is re-elected, the bulk of it will roll out on schedule in 2014.

Essential Fact

That’s the essential fact because, unlike Mitt Romney’s tax reform proposal or Obama’s deficit-reduction plan, voters can truly count on it. If Obama is re-elected, every American making less than 133 percent of the poverty line will receive Medicaid (sorry, but I don’t buy that even the reddest of states will long resist a 9-to-1 ratio of federal-to-state Medicaid funding); every American making between 133 percent and 400 percent of the poverty line will get tax credits to help them buy private insurance; and there will be an expectation — reinforced by a tax penalty — that Americans who can buy quality health insurance for less than 8 percent of their income will do so.

If Obama is re-elected, Americans who lose their jobs needn’t fear that their families will lose their health insurance. Discrimination based on pre-existing conditions will be a thing of the past and every state will have a health insurance exchange where insurers compete for business and where regulators can expel shoddy health plans. Medicare will transition from its fee-for-service model toward a system of value-based payments in which providers are compensated for maintaining healthy patients. Expensive employer-based health plans will be slapped with a hefty tax beginning in 2018.

If Obama is re-elected, in other words, we will see the first iteration of a uniquely American universal health-care system. If history is any guide, it will become effectively permanent soon after it is introduced. The reforms will be reformed, of course, as experience teaches us what works (and what doesn’t) and as future politicians put their stamps on the system. But the basic guarantee — that the state will provide health insurance or subsidies to purchase it for those in need – – will likely prove immutable.

If Romney wins, by contrast, the Affordable Care Act will probably be fully or largely repealed, with no clear prospect of a replacement. Admittedly, that’s a somewhat more tenuous prediction, as President Romney might well need to negotiate with a Democratic Senate that’s not much interested in overturning its signature health-reform law. But if Romney wins and Democrats still hold the Senate, they’re unlikely to have a cushion of more than a vote or two. It’s possible that the Senate’s most conservative, endangered Democrats will resist Romney’s call for repeal or insist on a genuine replacement for the law, but I wouldn’t bet much money on it.

Safety Structure

In addition to being the central policy at stake in this election, the Affordable Care Act is the centerpiece of Obama’s legacy. If he’s reelected, he will go down in history as the president who finally provided almost every American with health insurance. That’s enough to elevate him to the pantheon of transformative presidents. “Obamacare” will join Medicare and Social Security as essential struts in the nation’s social safety structure.

If he loses, he will go down in history as a one-termer who gambled and lost on universal health care. As often happens when history revisits failed legislative initiatives, the law will look more bungled and reckless in retrospect. Historians will criticize the Obama administration for pursuing health-care reform in the midst of an economic crisis. Republicans, who will likely benefit from a stronger economy as deleveraging subsides — which will also aid Obama if he wins — will argue that the repeal of Obamacare lifted uncertainty and ignited a recovery.

It seems absurd that the line between a transformational presidency and Jimmy Carter II might be a sliver of one percent of the vote in Ohio. That doesn’t mean it isn’t true.

Which is all to say that yes, this election matters more than most. It matters more politically because the party in power will probably see its agenda affirmed by a cyclical recovery. But it matters more to actual people because the Affordable Care Act is poised to reshape American health care in two years. A vote for Obama is a vote for the law to take effect and for 30 million Americans to get health insurance they won’t get otherwise. A vote for Romney is a vote for the law to be repealed. There are few elections in which the stakes are so clear.