Obamacare will be a huge voting issue for Republicans — that’s already clear. They’ll turn out in droves because they hate the law. What’s less clear is how Democrats will get their supporters to the polls to say, “hey, thanks for health reform.”

And yet, the Affordable Care Act only exists because Democrats and their supporters had pushed for health reform for decades. Republicans didn’t ask for it. Independents didn’t demand it. It was liberals who wanted coverage for the uninsured, and a better system for sick people, to plug what they saw as the last remaining hole in the social safety net.

( Also on POLITICO: The Obamacare report card)

Now it’s here, and as clumsy as the rollout was, it’s the law they wanted. So the task for Democrats is to figure out how to close the enthusiasm gap — and convince their voters that Obamacare should be a voting issue for them, too.

The reality is, it’s probably going to be a negative message rather than a positive one. Most Democrats believe they can motivate voters by shifting the conversation to the GOP repeal efforts — warning voters about all the things they’d lose if the law went away.

In their view, the best campaigns will be laser-focused on how bad the old health care system was for many patients, and hammer away at Republicans as defenders of the old status quo.

“Democrats will turn out to prevent Republicans from giving insurance companies the power to raise health care costs, raising the costs of prescription drugs for seniors, and leaving kids with pre-existing conditions out in the cold,” said Democratic Congressional Campaign Committee Chairman Steve Israel. “We win by reminding voters of the catastrophic costs of repeal.”

The rapid surge of last-minute signups will help — it will make it easier for Democrats to prove there’s real interest in the law. At some point, though, they’ll have to deal with the awkward part that’s on everyone’s minds: How much do you actually talk about the botched website and the canceled policies?

( CARTOONS: Matt Wuerker on Obamacare)

Increasingly, liberal Democrats and outside groups are convinced that the formula that party strategists had recommended until now — telling candidates to stress that they’ll fix what’s wrong with the law — is not going to work. Instead, they’re saying vulnerable Democrats need to declare that millions of people have coverage now, remind everyone how bad the old system was, and accuse Republicans of wanting to return to it.

They can acknowledge the problems with the website, the thinking goes, but it should be a side note, not the start of the conversation with voters.

“You’ve got to be unapologetic about supporting it, because if you’re not, you don’t motivate people to come out and vote,” said Brad Woodhouse, president of American Bridge PAC and Americans United for Change.

Liberal Democrats say the “no apologies” strategy is one lesson of the Florida special election this month, in which a weak Republican candidate, David Jolly, won with appeals to anti-Obamacare voters while Democrat Alex Sink lost with the standard “fix what’s bad, keep the good” formula.

( VIDEO: Timeline of Obamacare deadlines)

“You’ve got to run a populist campaign, you’ve got to run the kind of campaign that really gets Democrats excited” — and one way to do that is to remind liberals that the law can be “a building block for better health care in the future,” said Mike Lux, co-founder of the consulting group Progressive Strategies.

Party officials, however, still say Democratic candidates have to talk about the law’s problems head-on, because that’s what voters want to hear about. They’re under no illusions that the rollout went well.

That’s the model Sens. Mary Landrieu of Louisiana, Mark Begich of Alaska, and Mark Warner of Virginia are using as they run for re-election this year. They’re teaming up on a package of changes to the health care law, along with Heidi Heitkamp, Angus King, and Joe Manchin. They all say the law is better than the old health care system, but their proposal sends a different message: that the law is “not perfect,” in their words, and can be improved.

All Democrats agree, though, that the most important motivator is to tell voters how vulnerable their health care could be if the law was repealed. Most polls show that a majority of Americans want to give the law a chance rather than repealing it. So that’s one area where Democrats would have an advantage — if they could get those people to show up on election day.

“Most Americans don’t support repeal. They want to fix and improve the law,” said Israel.

( Also on POLITICO: Poll: Obamacare fails to gain support)

The greater intensity of Republican voters is no surprise when you take a close look at the polls. People who don’t like the health care law are just more worked up about it than those who like it. In a Pew Research Center poll this month, the largest single group was the one that doesn’t just disapprove of the law, but “very strongly” disapproves of it — 41 percent of the people in the survey. That group includes 79 percent of Republicans, but also 44 percent of independents.

By contrast, just 53 percent of Democrats “very strongly” approve of the law — and only 19 percent of independents feel that way.

The Democrats also have a unique problem: In a CNN/ORC International poll earlier this month, 12 percent of Americans said they oppose the law not because it goes too far, but because it’s “not liberal enough.”

The enthusiasm gap isn’t a direct threat to the law’s survival right now — even if Republicans win control of the Senate. They’ll be able to push more votes to knock out or delay parts of the law, or even repeal it or defund it, but as long as President Barack Obama is in the White House, the Affordable Care Act will stay on the books.

But those votes will allow the drumbeat of anti-Obamacare votes and investigations to get even louder. And if Democrats can’t turn public opinion around soon, they’ll have to deal with the enthusiasm gap all over again in 2016 — this time when they’re trying to hang on to the White House.

“As long as Barack Obama is the president, it’s going to be the law of the land. So we’ll have three years of real experience with the law. That will be a fair test,” said William Galston, a domestic policy expert at the Brookings Institution and a former adviser to President Bill Clinton.

But after three years, “if it’s still staggering along, there will at least be major changes,” Galston said — and if Republicans sweep the White House and Congress in 2016, “the surgery might be very radical indeed.”

Democratic strategists point out that it won’t be any one issue that drives people to the polls. But they’re still privately cringing at how the rollout went, and they’re furious at Health and Human Services Secretary Kathleen Sebelius and other officials whose job was to get it right.

“Even though the website is working, the stench of the rollout lingers. Sebelius’s screw up will almost certainly cost us a bunch of seats,” said one Democratic operative. “But in time — certainly going into 2016 — the politics of the ACA will change. People do not like to lose benefits once they have become accustomed to receiving them. Why do you think the Dems never fundamentally changed or repealed the Bush prescription drug entitlement?”

That’s why Democratic campaign officials want to put so much focus on what would happen if the nation went back to the old health care system. Until now, they’ve spent more time trying to find success stories of newly insured, happy people. But for the elections, they’re leaning toward a different approach: finding horror stories of people who used to get turned down for health insurance or bankrupted by an illness, and having them say in TV ads, “Don’t make me go back to that.”

Democratic pollster Mark Mellman points out that the newly insured people haven’t had a chance to show whether they will be committed voters yet. “If you can communicate with them and explain what they stand to lose if the law is repealed, that will make a difference,” he said Mellman. “By November, we’ll be in a different position with those folks.”

Republicans will insist that a return to the status quo isn’t their plan, and that they’ll have other ideas to lower the cost of health coverage without Obamacare’s problems. “The Democrats’ poor spin here is reflective of the fact that they simply have nothing to say here, and they know it,” said Brad Dayspring, a spokesman for the National Republican Senatorial Committee.

But it will be harder to make that case if House Republicans can’t agree on a health care alternative to vote on, and it will be easy for Democrats to boil their ads down to a simple choice: Obamacare or the bad old days.

Even if that works, it’s increasingly unlikely that the health care law will follow the model Democrats have always hoped for — becoming as popular as Social Security and Medicare after people started getting the benefits, according to the University of North Carolina’s Jonathan Oberlander, who has written about the political history of Medicare.

“I don’t believe it’s ever going to have quite the same hold as Medicare or Social Security,” Oberlander said. “Those are social insurance programs, where everyone pays in and gets the benefits. The Affordable Care Act is much more diffuse … and it’s more difficult to mobilize people around it.”