Under heavy Republican attack, Democrats in the House of Representatives on Tuesday defended plans to pass a healthcare overhaul without a direct vote as President Barack Obama's top domestic priority neared a make-or-break showdown.

Obama and House Democratic leaders lobbied undecided Democrats for support ahead of a possible weekend vote on the overhaul, which would constitute the biggest change in the $2.5 trillion U.S. healthcare system in four decades.

Democrats are considering using a complicated process to avoid a direct vote on the Senate-passed bill, which is unpopular with House Democrats. Instead, they would declare the Senate bill passed once the House votes to approve changes it wants.

Republicans said the strategy was designed to protect Democrats in November's congressional elections by camouflaging their vote. There is no way to hide from this vote, House leader John Boehner said. You can run but you can't hide.

Democrats noted Republicans used the process when they controlled the House and accused them of trying to change the subject. If you don't want to talk about substance, talk about process, House Speaker Nancy Pelosi said of Republicans.

Representative Chris Van Hollen, chairman of the Democratic House campaign committee, said the procedure was perfectly appropriate and he was not concerned about a political backlash.

At the end of the day, what the American people are going to look at is what this bill does to affect their daily lives, he told reporters.

Pelosi said there would be no decisions on procedure until the Senate bill's changes are done. Democrats have struggled to find a combination that will win support and lead to favorable cost estimates from the Congressional Budget Office.

Democratic House leaders worked on the overhaul into the night in Pelosi's office, and Pelosi also met with Senate Democratic leader Harry Reid. House leaders told Democrats to expect votes on either Saturday or Sunday.

House Democratic Whip James Clyburn, the top Democratic vote-counter in the House, told Fox News that Democrats still do not have the 216 votes needed for passage but he was confident of getting there.

'WE'LL GET THERE'

I do not have 216 commitments yet, though I think we'll get there in time for the vote, Clyburn said.

The overhaul would extend coverage to more than 30 million uninsured Americans and ban insurance practices like refusing coverage to those with pre-existing medical conditions.

Health insurer shares were up on Tuesday slightly more than the broader market. The Morgan Stanley Healthcare Payor index was up 1.6 percent and the S&P Managed Health Care index rose 1.3 percent.

As many as two dozen undeclared Democrats could decide the overhaul's fate, which has been the focus of a political brawl that has consumed the U.S. Congress for months.

Representative Jason Altmire, who voted against the overhaul in November but is undecided this time, said he has spoken to Obama three times in the last 10 days, including a 10-minute phone conversation on Monday.

When the president takes the time to personally reach out, it makes an impact, he told reporters. He said he also heard from several Cabinet officers.

Altmire said the voting procedure being considered by House Democrats would be a negative factor in his evaluation, although other undecided Democrats said it did not matter.

The media is really focused on process. Most of us are focused on substance, said Representative Jerry Connolly, another undecided Democrat.

A new NBC/Wall Street Journal poll showed the public is split on the reform plan, with 46 percent saying it would be better to pass Obama's plan and 45 percent preferring to keep the system as it is now.

But supporters argued House Democrats, who passed an initial version of the overhaul in November with three votes to spare, should go ahead and finish the job or they could face dire consequences in November's elections.

If we pass this bill, we will be judged by the results, Democratic Representative Jerrold Nadler said. If we don't pass this bill, we will be judged by the accusations.

Republicans have condemned the health bill as a costly government takeover that would lead to higher insurance premiums and less consumer choice.

Under the procedure planned for passing the reform overhaul, the House would approve the Senate's version of the bill. The changes sought by Obama and House Democrats would move through a separate measure.

The House changes would then be approved by the 100-member Senate under budget reconciliation rules that require only a simple majority, bypassing the need for 60 votes to overcome Republican procedural hurdles.

I feel confident that once the House does its work, we will take care of things over here, Reid told reporters.

(Additional reporting by Thomas Ferraro; editing by David Alexander, Todd Eastham and Bill Trott)

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