WASHINGTON -- President Barack Obama and congressional Democrats, holding out little hope for today's televised bipartisan summit on health care, are prepared to try for a far-reaching bill in the coming weeks without a single Republican vote.

Barring an unexpected two-party breakthrough at the summit, Democratic leaders feel they can't afford to fail, leaving them empty-handed on a huge priority in an already difficult election year.

It's far from clear that they can gather the votes, however, and it will take a major effort to unite fractious Democrats.

A bipartisan compromise seems highly unlikely, members of both parties said Wednesday. Popular insurance reform measures, which Republicans might support, require Democratic-backed measures the GOP staunchly opposes, such as government subsidies to enable millions of low-income Americans to buy health coverage.

With Democrats unwilling to start from scratch, "I think it's nearly impossible to imagine a scenario under which we could reach an agreement," said Senate Minority Leader Mitch McConnell, R-Ky., who will attend the televised six-hour meeting across from the White House.

The summit will be aired live on C-SPAN, with other news networks providing extended coverage throughout the day.

Given such comments, Democratic leaders said they hope to persuade House Democrats to swallow their objections and approve a health bill the Senate passed on Christmas Eve. In return, Senate Democrats would have to agree to make various changes to health care laws under budget reconciliation rules, which bar GOP delaying tactics.

"Tomorrow we'll have that meeting, .... but far more important after that meeting, you can either join us or get out of the way," Sen. Chris Dodd, D-Conn., said at a rally Wednesday.

While deriding the summit, Republicans plan to focus on six main areas, according to congressional aides -- state incentives to lower costs, making insurance affordable to those with pre-existing conditions, purchasing health insurance across state lines, ending frivolous lawsuits, small business health plans, and expanding health savings accounts.

The House in November passed its version of the health care overhaul 220-215, with 39 Democrats abandoning their party's leaders. Those leaders now fear that they will lose even more votes over an abortion dispute, and it's unclear whether they can persuade enough of the 39 to come on board to make up the difference.

Democrats easily came together on one of the more popular health care issues Wednesday, as the House voted overwhelmingly to repeal the health insurance industry's exemption from federal antitrust oversight. The vote gave Democrats a win on the eve of the summit.