WASHINGTON -- Democratic leaders scrambled Sunday to pull together enough support in the House for a make-or-break decision on health care reform later this week, expressing optimism that a package will soon be signed into law by President Barack Obama despite a lack of firm votes for passage.

The rosy predictions of success, combined with the difficult realities of mustering votes, underscore the gamble that the White House and congressional Democrats are poised to make in an attempt to push Mr. Obama's health care plans across the finish line. The urgency of the effort illustrates growing agreement among Democratic leaders that passing the legislation is key to limiting damage to the party during this year's perilous midterm elections.

But House Minority Leader John Boehner, R-Ohio, pledged to do "everything we can to make it difficult for them, if not impossible, to pass the bill." He also joined other Republicans Sunday in warning that Democrats would pay for the legislation by losing even more seats than expected in November.

The most optimistic talk on Sunday came from the White House. Senior Obama adviser David Axelrod predicted that Democrats "will have the votes to pass this," and press secretary Robert Gibbs declared that "this is the climactic week for health care reform."

But Rep. James Clyburn, D-S.C., the Democrats' chief head-counter in the House, cautioned that the party has not yet found the 216 votes needed to win approval of the health care bill passed by the Senate in December.

"We don't have them as of this morning, but we've been working this thing all weekend," Mr. Clyburn said on NBC's "Meet the Press." "I'm also very confident that we'll get this done."

Democratic leaders are struggling to assemble support amid opposition to the Senate legislation from conservative Democrats, who object to abortion-related language in the bill, and from liberals, who are disappointed about the lack of a public insurance option and other measures. Mr. Obama has postponed a trip to Indonesia and Australia to help whip up support for the package.

Republicans pressed ahead Sunday with a battery of arguments against the Democratic plans, saying that polls show firm public opposition to the legislation and that Senate leaders are using parliamentary gimmicks in an attempt to win final passage. Sen. Lindsey Graham, R-S.C., who has signaled a willingness to work with the administration on immigration and detention issues, said Mr. Obama's "arrogant" push for health care reform has divided the country and threatens bipartisan cooperation.

"When it comes to health care, he's been tone-deaf, he's been arrogant and they're pushing a legislative proposal and a way to that legislative proposal that's going to destroy the ability of this country to work together for a very long time," Mr. Graham said on ABC's "This Week."

The Democrats' strategy calls for the House to pass the Senate version of reform, followed by consideration of a package of fixes to that legislation known as a reconciliation bill. The fixes must meet specific budget requirements allowing it to be approved in the Senate with a simple majority vote. The approach avoids having to muster 60 votes to overcome a threatened GOP filibuster; Democrats control 59 seats.

House Democrats expect to receive a final cost estimate by this afternoon, when the House Budget Committee is scheduled to vote on the reconciliation package. It would then go to the House Rules Committee, where Chairman Louise Slaughter, D-N.Y., could package it with the $875 billion measure the Senate passed on Christmas Eve. The package is also expected to include Mr. Obama's proposed overhaul of the student-loan system.

The full House is expected to vote on both measures by week's end, aides said.

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.