– The war over health care is being waged all over again.

Supporters and opponents of the Affordable Care Act — also called Obamacare —are battling for American eyeballs in an advertising and outreach war, reminiscent of the 2009 political fight when Congress debated the legislation.

The two sides will spend $500 million trying to persuade citizens to embrace or defy the law in the next few months and through early next year, according to industry publication Ad Age. That’s because President Obama’s sweeping health care plan will move from theory to reality for millions of Americans as the online marketplaces, where people buy insurance, open in October.

Groups without the means or the expertise to launch ads are finding their own way to grab attention.

The conservative Heritage Action for America is hosting the Defund Obamacare Town Hall Tour.

“The goal is to thwart the administration’s drive to get millions of people into the exchange by April. We hope to hasten the collapse of the exchanges by educating young adults as to why Obamacare is a raw deal for them,” said Dean Clancy, vice president of health care policy at FreedomWorks, another conservative organization.

The liberal group Protect Your Care is staking out town hall meetings hosted by congressional Republicans who want to stop funding for the law.

And nurses from the SEIU, the largest health care union in North America, are leading outreach efforts to educate their patients and others about the law in time for the enrollment opening.

Time is running out for those who want to repeal the law before any more significant benefits take effect.

“This is really why you’re seeing and hearing the last gasp of Republicans trying to repeal the law,” said Brad Woodhouse, president of Americans United for Change.

Once Americans get a look at the full benefits under the law, repeal is “going to be impossible to do,” he said.

Many conservatives agree they must act now.

The organization FreedomWorks created an Obamacare card, designed to look like a 1960s-era draft card, and is holding Obamacare card-burning parties. While the group takes video, it encourages young adults, in particular, to burn their Obamacare card and to pledge not to buy insurance through the marketplace.

Twenty- and 30-somethings are particularly desirable to both sides of the debate. In order to keep ­premiums from skyrocketing, young people must sign up for coverage to balance out older Americans and those who are already ill, who are expected to flock to guaranteed health coverage.

The push to reach out to young Americans is part of a three-pronged strategy to “reverse the Washington health care takeover,” Clancy said. “We call it defund, delay and defy.”

His group is working with a handful of members of Congress, including Florida Sen. Marco Rubio, who propose shutting down the government if they can’t get Congress to pass a budget withdrawing funding for the health care law.