"The sales pitch is simply that we're on the cusp of the type of health care reform that this country has been talking about for decades," said Robert Gibbs. "Do this for the country. Do this for your constituents."
Democratic House Speaker Nancy Pelosi said only Republican delaying tactics could put off a vote Saturday on the 10-year, 900-billion-dollar measure -- the most ambitious overhaul of its kind in a half-century.
Democratic House Majority Leader Steny Hoyer said he had cautioned lawmakers that there is a chance the final ballot could occur Sunday, Monday, or Tuesday but that "we're very close" to having the 218 votes needed.
Democrats were still wrestling with intra-party feuds over banning government funding for abortions and over restrictions aimed at ensuring that undocumented immigrants do not have access to the new benefits.
As Obama prepared for his Saturday charm offensive, he tasked Vice President Joe Biden with the job of calling wavering lawmakers as Democrats worked to put together the 218 votes needed to win House approval of the package.
Even if Democrats squeeze the measure through, it must still clear the Senate, where Democratic Majority Leader Harry Reid faces more daunting obstacles and has hinted any action could slip to 2010.
That would put the issue front-and-center in the 2010 mid-term elections, when one third of the Senate, the entire House of Representatives, and many US governorships are up for grabs.
Gibbs played down that potential headache, saying lawmakers would "ultimately, we believe, before the end of the year get a bill to the president's desk" and that Obama "sees tomorrow as an important step forward."
Republicans, united in opposing the plan, crowed privately that the last-minute scramble to schedule Obama's visit and the vote showed that Democrats were short of the numbers needed to pass the measure.
House Minority Leader John Boehner said the grim news that US unemployment had soared to 10.2 percent, the highest level since 1983, showed the need to defeat "this job-killing bill."
On Thursday, the number two Republican in the House, Eric Cantor, promised several thousand protestors at the US Capitol that "not one Republican will vote for this bill."
Looking to secure what would be a major victory for the White House, its independent political arm, Organizing for America, urged supporters to call lawmakers warning the final outcome could rest on "a single vote."
Democratic Representative Louise Slaughter, chairwoman of the House Rules Committee that will shape the final bill and the rules for debate, said "we're all right" in the effort to reach 218 votes but declined to offer details.
The United States is the only industrialized democracy that does not ensure that all of its citizens have health care coverage, with an estimated 36 million Americans uninsured.
And Washington spends vastly more on health care -- both per person and as a share of national income as measured by Gross Domestic Product -- than other industrialized democracies, according to the Organization for Economic Cooperation and Development.
The United States spent about 7,290 dollars per person in 2007, more than double what Britain, France, and Germany, with no meaningful edge in the quality of care and lags behind OECD averages in life expectancy and infant mortality.
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