WASHINGTON — Newly released figures show enrollments for coverage under President Obama's healthcare plan fell far below official projections, underscoring the damage inflicted by the botched rollout and further endangering the administration's support among restive Democrats on Capitol Hill.

Just 106,185 Americans successfully enrolled in health coverage in October. The administration had hoped to get half a million people signed up in Obamacare's first month. About a third of the enrollments — 35,364 — came from California.

To head off a revolt among lawmakers, White House officials said Wednesday they would have a plan soon — perhaps by Thursday — to help millions of Americans whose current health plans are being canceled because they don't meet the law's standards.

Administration officials also sought to reassure doubters that the online marketplaces created by the law would be viable, emphasizing strong consumer interest in shopping for health insurance through the Affordable Care Act.

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Nationwide, nearly 1.1 million people have been approved to get insurance through one of the new marketplaces but have not yet chosen a plan, the Department of Health and Human Services reported. An additional 396,000 have qualified for Medicaid and the Children's Health Insurance Program.

The Obama administration hopes to enroll 7 million people in new state-based marketplaces by the March 31 deadline.

But whether the administration can hold nervous Democrats in line much longer is unclear.

Anxious congressional Democrats have become increasingly panicked by the problematic debut of the president's signature domestic policy achievement as they head into the 2014 election.

Rep. Raul M. Grijalva (D-Ariz.), a leader of the progressive wing in the House, called the enrollment numbers "disappointing."

"What it shakes my confidence in is the ability to pull it off, which is essential to this whole thing," he said. "I can go out and debate the substance of this with anybody. I can't defend or debate the programming, or our inability to make this thing work the way it was promised it would work."

Democratic worries have been galvanized by the insurance policy cancellations, which conflict with a promise Obama repeatedly made that people would be able to keep plans they liked.

Republicans have promised to make Obamacare a defining issue in next year's campaigns.

House Republicans will press forward Friday with a vote that will be tough for many Democrats to oppose. The bill from Rep. Fred Upton (R-Mich.) would allow insurance companies to continue to offer policies on the individual market that don't meet new standards set by the Affordable Care Act.

Democratic uneasiness was underscored when Rep. Carol Shea-Porter of New Hampshire announced her support for the bill. The Democrat lost her reelection bid in 2010 after voting for the healthcare law, but won again in 2012. "Some aspects of the ACA need to be fixed," she said.

Rep. Steve Cohen (D-Tenn.), who is in a relatively safe district, expressed the anxieties of many Democrats. "It puts us in a political bind: We voted for the bill, we supported the bill, we supported the president — frankly, a lot of people in the caucus don't think they're getting nearly as much support from the White House," he said.

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Sen. Mary L. Landrieu (D-La.), in a tough reelection battle, picked up more Democratic sponsors of her legislative fix for the cancellation problem, and Sen. Mark Udall (D-Colo.), who is also up for reelection, announced a similar proposal Wednesday. Sen. Jeanne Shaheen (D-N.H.), who is seeking a second term, introduced a bill Wednesday that would postpone the March 31 deadline for enrollment until the website is improved.

The Obama administration has resisted pressure to make substantive changes to the law, arguing that the program is beginning to work.

"In every part of our country, Americans are very interested in the affordable health coverage that is being offered through the marketplace and through Medicaid," Health and Human Services Secretary Kathleen Sebelius said. "Even with the issues we've had, the marketplace is working and people are enrolling."