DENVER — Healthcare reform may be taking a back seat on the stage of the Democratic National Convention, but liberal activists are fighting to make sure it is center stage during the presidential campaign.

Before the advent of $4-a-gallon gasoline this year, Democrats thought healthcare would be at the head of the domestic agenda this election year.

Healthcare has not been absent from the convention, though other issues have eclipsed it.

To be sure, prominent Democrats such as Sens. Hillary Rodham Clinton (N.Y.) and Edward Kennedy (Mass.) have highlighted healthcare reform in their high-profile speeches at the convention, and Obama is sure to do the same Thursday at Invesco Field.

“I cannot wait to watch Barack Obama sign into law a healthcare plan that covers every single American,” Clinton said Tuesday.

Kennedy said, “[T]his is the cause of my life — new hope that we will break the old gridlock and guarantee that every American — north, south, east, west, young, old — will have decent, quality healthcare as a fundamental right and not a privilege.”

If this week in Denver is any guide, liberal healthcare activists are not going to let the issue fade into the background. “It is important that the next president and the next Congress make healthcare reform a top and early priority,” said Ron Pollack, executive director of the influential liberal healthcare group Families USA.

Though the speeches by prominent Democrats and other official convention events at the Pepsi Center are the main focus of attention, lawmakers, liberal activists and allied groups are staging an ersatz convention of their own, taking the form of rallies, briefings, lunches and cocktail receptions across Denver.

There are about a half-dozen of these events each day on topics ranging from covering the uninsured to mental health to HIV/AIDS. In addition to the activist groups, corporate interests such as the drug maker AstraZeneca and lobbying groups like the Pharmaceutical Research and Manufacturers of America are getting in on the game.

Clinton and a host of prominent Democrats have appeared at these events, including House Energy and Commerce Committee Chairman John Dingell (Mich.), Massachusetts Gov. Deval Patrick, Kansas Gov. Kathleen Sebelius, San Francisco Mayor Gavin Newsom and former Sen. Tom Daschle (S.D.).

Political conventions are primarily about showcasing the party’s candidate for president, but they’re also about highlighting the issues the party believes will win them votes, and healthcare skews favorably toward Democrats. Healthcare also can be cast as a classic pocketbook issue for middle-class voters who keep seeing their health insurance and medical care become increasingly expensive.

“I don’t think any Democrat can have a successful campaign and not address [healthcare],” said Rep. Marion Berry (D-Ark.), a former pharmacist.

“It actually highlights a very significant difference between the proposals of Sen. McCain and Sen. Obama,” Pollack said.

“McCain is repackaging the failed policies of the past,” said Service Employees International Union (SEIU) President Andy Stern. Families USA and the SEIU have been particularly active in Denver this week, staging several briefings and rallies between them.

The timely release of the latest census figures on the number of people without health insurance has added fuel to the fire. Though down slightly to 45.7 million, Obama seized on the numbers to criticize Bush and McCain.

In spite of the enthusiasm of activists, though, and the rhetoric of politicians, the left wing remains deeply divided about healthcare reform.

On Tuesday evening, about 150 people gathered at the Denver Convention Center to honor House Judiciary Committee Chairman John Conyers Jr. (D-Mich.), the chief sponsor of a bill that would replace the private healthcare system with a single-payer, government-financed system.

Single-payer healthcare is a dream of the left and a boogeyman to the right. Obama eschewed this approach in favor of a plan that would seek to preserve the private healthcare market.

Conyers takes a different view. “Capitalism is a wonderful thing, but it shouldn’t be in healthcare,” he said at the reception, which was hosted by the California Nurses Association, the National Nurses Organizing Committee and the Progressive Democrats of America.

Berry occupies the other end of the spectrum within the party. “We don’t have the money to create some grand scheme where the government pays for everybody’s healthcare without just massively raising taxes. I don’t know anybody that thinks that’s even remotely possible. I’m certainly not interested in that,” he said.