WASHINGTON — If there's a rhetorical knockout blow out there in the fight over health care, neither side has found it.

President Barack Obama and his opponents are searching for bite-sized, focused and compelling messages that will win over the voters who polls show remain up for grabs.

Obama and his foes are going at it hard during the congressional break in August, a raucous, pivotal month when the public and lawmakers are deciding whether to support his drive to reshape the health system.

At a town hall meeting this past week in Portsmouth, N.H., Obama said, "If you don't have health insurance, you will finally have quality, affordable options once we pass reform. If you do have health insurance, we will make sure that no insurance company or government bureaucrat gets between you and the care that you need."

He said people could keep their current doctors and health plans and not have to wait in lines. He promised his plan would help the economy without worsening the federal deficit. He denied it would encourage euthanasia of older people or cuts in their Medicare coverage.

His comments — a jumble of playing offense and defense — showed how tricky it is to concisely explain how people would benefit from reshaping the $2.5 trillion health system. The search for the right message is complicated by all those who, according to polls, like the general idea of an overhaul but are fairly satisfied with their own health coverage.

Obama and his strategists are "on their heels a little bit right now, but I don't think it's a permanent condition," said Chris Jennings, a Democratic lobbyist. He advised President Bill Clinton on health care and was among several Democrats who said the White House message must get clearer. "I think they're recalculating and refocusing."

Republicans and other opponents have had it easier, in a way. It usually is simpler to attack than defend. Most notably, they have sprinkled their advertising and speeches with familiar, poll-tested catch-phrases.

A TV ad the U.S. Chamber of Commerce just began airing in about 20 states warned of "inflated taxes, swelling deficits and expanded government control over your health." House GOP leaders sent lawmakers home for the summer break with packets lambasting Obama's "government takeover of health care."

Former hospital executive Rick Scott, who heads the big-spending Conservatives for Patients' Rights, distributed a memo citing "less choice, long waiting lists and denial of needed treatments for patients."

Such attack lines have a strong appeal to conservatives who comprise the core of the GOP. It is unclear how persuasive they are to centrist voters.

"What you're watching is a developing process" in which both sides are refining their messages, said David Winston, a GOP pollster who has worked with his party's congressional leaders. "This issue has been extraordinarily difficult to understand over the years."

Supporters and opponents have been preparing their health messages for a long time, relying on polling, focus groups, testing of ads and plain old experience.

Reflecting a consensus that Democratic rhetoric during Clinton's failed health care effort of 1993 and 1994 focused too heavily on the uninsured, the White House has stepped up arguments that its proposals would help those already covered.

Every word can make a difference. Democrats talk about "affordability," not "cost containment," which might suggest cuts in services. "Coverage for all" is better than "universal" coverage, which has echoes of government-controlled care.

Resurgent Republic, a GOP strategy organization, is advising Republicans to focus on concerns that a health overhaul could increase budget deficits, raise taxes and push people into government-run coverage. The group is urging Republicans to propose alternative proposals — they have offered several — because people's top economic worry is their rising health costs.

During Congress' August vacation, those opposed to an overhaul have disrupted lawmakers' town hall meetings. Many see it as a crucial month as legislators gauge whether the uproar is orchestrated — as Obama backers insist — or if people are lumping the roughly $1 trillion health effort together with the unpopular Wall Street and Detroit bailouts and the economic stimulus package into a gigantic symbol of big government run amok.

In an interview, senior Obama adviser David Axelrod said the public thinks changes are needed and the White House has a strong argument to address that desire.

"If I had one line to say, it's that we want to bring stability and security to health care so people could know they can count on it and it will be there when they need it," he said.

For both sides, the weeks are dwindling to get their messages right.