WASHINGTON — If there is any doubt that President Obama's plan to overhaul U.S. health care is the hottest topic in Congress, just ask the 3,300 lobbyists who have lined up to work on the issue.

That's six lobbyists for each of the 535 members of the House and Senate, according to Senate records, and three times the number of people registered to lobby on defense. More than 1,500 organizations have health-care lobbyists, and about three more are signing up each day. Every one of the 10 biggest lobbying firms by revenue is involved in an effort that could affect 17 percent of the U.S. economy.

These groups spent $263.4 million on lobbying during the first six months of 2009, according to the Center for Responsive Politics, a Washington-based research group, more than any other industry. They spent $241.4 million during the same period of 2008. Drugmakers alone spent $134.5 million, 64 percent more than the next biggest spenders, oil and gas companies.

"Whenever you have a big piece of legislation like this, it's like ringing the dinner bell for K Street," said Bill Allison, a senior fellow at the Sunlight Foundation, a Washington-based watchdog group, referring to the street in the capital where many lobbying firms have offices.

HEALTH STOCKS GAIN

Health-insurer and managed-care stocks have gained this year, led by WellCare Health Plans Inc., based in Tampa, Fla.; Cigna Corp., based in Philadelphia; and Coventry Health Care Inc., a Bethesda, Md., company. The three paced a 13 percent increase in the Standard & Poor's Supercomposite Managed Health Care Index since Jan. 1. Drugmaker shares have stagnated.

Health care lobbyists said their efforts are the biggest since the successful 1986 effort to overhaul the tax code. The result is a debate involving thousands of disparate voices, forcing Congress to pick winners and losers.

"There's a lot of money at stake and there are a lot of special interests who don't want their ox gored," Allison said.

The lobbyists are on all sides of the issue. Pharmaceutical Research and Manufacturers of America, the Washington-based trade group for drug companies such as Thousand Oaks, Calif.-based Amgen Inc. and New York-based Pfizer Inc., has embraced a health care overhaul.

SHAPING POLICY

Lobbying by Amgen, the world's largest biotechnology company, is intended to "effectively shape health-care policy," said Kelley Davenport, a spokeswoman. Pfizer, the world's largest drugmaker, is "dedicated to insuring that our voice is heard," said spokesman Ray Kerins.

The Washington-based U.S. Chamber of Commerce, the nation's largest business lobby, is opposing efforts to offer government- run health insurance to compete with private companies. The chamber spent $26 million in the first six months of 2009 to lobby, more than any other group.

For lobbyists, the goal is to ensure that whatever measure eventually becomes law doesn't cripple the industry they represent.

"They assume health care reform is going to happen and they want to be protected," said John Jonas, of the lobbying firm of Patton Boggs LLP in Washington.

Patton Boggs, the top lobbying firm in terms of revenue, has three dozen clients in the health care debate, including New York-based Bristol-Myers Squibb Co., and Bentonville, Ark.- based Wal-Mart Stores Inc., more than any other lobbying firm.

REFORM NEEDED

Brian Henry, a spokesman for Bristol-Myers, maker of the world's No. 2 best-selling drug Plavix, said the company wants to ensure any legislation preserves incentives for innovation.

"We believe the health-care system needs to be reformed and we've specifically supported an employer mandate and cost-containment measures," said Greg Rossiter, a spokesman for Walmart, the largest U.S. employer.

The lobbyists fill the appointment books of lawmakers, and line up at House and Senate office buildings. The staff of Senate Finance Committee Chairman Max Baucus, a Montana Democrat, rotates weekly meetings among the various groups in the health care debate, providers one week, purchasers a second, consumers a third.

"We hear from lobbyists all the time," said Representative Frank Pallone, a New Jersey Democrat who heads the House Energy and Commerce health subcommittee.

The blitz by lobbyists carries a risk for the public, said Larry McNeely, a health care advocate with the Boston-based U.S. Public Interest Research Group.

RISKING DELAYS

"The sheer quantity of money that's sloshed around Washington is drowning out the voices of citizens and the groups that speak up for them," said McNeely, whose group backs a public health plan, which Obama and many Democrats consider a centerpiece of any proposal and most Republicans oppose.

The lobbying push also risks delaying legislation, said Rogan Kersh, associate dean at New York University's Wagner School of Public Service.

"That amount of activity is inevitably going to slow down the process," Kersh said.

The quest for influence isn't limited to lobbying. Health care advocates have spent $53 million on commercials, according to Arlington, Virginia-based TNS Media Intelligence/Campaign Media Analysis, which tracks advertising spending.

The health care industry also contributed $20.5 million to federal candidates and the political parties during the first six months of the year, according to the Center for Responsive Politics. Senate Majority Leader Harry Reid, a Nevada Democrat who is up for re-election next year, received $382,400, more than any other lawmaker.

"There is a cacophony going on with so much money and so many individuals hoping to shape the legislation," said Sheila Krumholz, executive director of the Center for Responsive Politics, a Washington-based research group.

The number of lobbyists could grow once Congress returns next month and resumes efforts to enact legislation by the end of the year.