The last prospect for a bipartisan deal on healthcare reform hangs on closed-door negotiations among six senators, but colleagues on both sides of the aisle are already signaling doubts over whether it can win broad support.

Members of the group have talked about cutting Medicare costs and taxing the highest-end insurance plans – those of more than $250,000, perhaps. More controversially, the group might also be considering jettisoning a public option – one of President Obama’s primary wishes – because it is a nonstarter for Republicans, in favor of health insurance cooperatives.

“We don’t know what’s going on in these delicate negotiations,” says Sen. Richard Durbin (D) of Illinois, the majority whip. “There’s high anxiety. We can’t say sight unseen if this will be something Democratic leaders can support.”

Republicans ready to start over

Republican leaders are already talking in terms of scrapping proposals to date.

“My guess is that, when it’s all said and done, we’ll come back in September and we’ll say, let’s start all over again,” says Sen. Jon Kyl (R) of Arizona, the Republican whip.

“We need to clear the decks here and solve specific problems with specific solutions that do not impose a government takeover and hurt … what most Americans can enjoy today,” he adds.

Trying to get it done

The team of Sens. Max Baucus (D) of Montana and Charles Grassley (R) of Iowa – the chairman and senior Republican on the finance panel, respectively – also hatched the compromise that moved the first Bush tax cuts through the Senate in 2001.

But the overhaul of America’s healthcare system is a vastly more complex undertaking.

“This is not one bill. It’s many, many, many, many, many bills,” Senator Baucus told reporters after a Democratic caucus luncheon Tuesday. Senators involved in the negotiations include Sens. Grassley, Olympia Snowe (R) of Maine, Michael Enzi (R) of Wyoming, Jeff Bingaman (D) of New Mexico, and Kent Conrad (D) OF North Dakota.

Responding to reports that the Finance committee may abandon a public option in favor of insurance cooperatives, Sen. Sherrod Brown (D) of Ohio said that "there is no real evidence we can put together a cooperative, scale it up, and make it work on a national level."

"They should keep working on a bipartisan plan but they ought to have a fallback, if they can't get Republicans on, that will command the support of majority of Democrats," said Sen. Carl Levin (D) of Michigan, who favors a public option.

"If you asked me to give you a definition of what cooperatives are, I couldn't," he added.

Last week, Sen. Orrin Hatch (R) of Utah pulled out of the group. “Some of the things they’re talking about, I just cannot support,” he said.

Stung by White House charges that they have become the “party of no,” Republicans say they are frustrated that GOP alternatives have gotten little traction.

House action stalls as Democrats feud

On the House side, the challenge is to overcome deep rifts in Democratic ranks. In a bid to rally support within their caucus, House Democratic leaders set up a marathon, five-hour tutorial this week to talk members through details of the vast draft bill.

The House Ways and Means Committee and the Education and Labor Committee have completed work on their bills. But conservative Democrats in the Energy and Commerce panel want to rein in the cost of the bill.

“[The Democratic] caucus is a diverse caucus. Sooner or later, the other views needed to be considered,” says Rep. Earl Pomeroy (D) of North Dakota, a member of the conservative Blue Dog caucus. “Had more of an effort been made to take these concerns seriously at an earlier point, the bill would be a better product.”