The health-care Web site’s improved performance has both U.S. political parties shifting strategies, with President Barack Obama’s team preparing a January advertising blitz and a wave of celebrity promotions to boost enrollment, allies said.

On Capitol Hill, Republican opponents of the health-care law are emphasizing new points of attack, highlighting examples of people who are paying more for insurance -- including House Speaker John Boehner, and those losing access to their doctors as they shift plans, congressional aides said.

Spirits among the president’s health-care advisers have been “significantly uplifted” this week, said Ron Pollack, executive director of Families USA, a Washington-based advocacy group with close ties to the administration. “There is a great deal of relief about how the website has been improved.”

The stakes riding on the rollout of the Patient Protection and Affordable Care Act are high: Obama’s presidential legacy and the U.S. Senate majority in 2014 midterm elections could hinge on public perceptions of the law.

The administration and supporters of the health law are determined to avoid tit-for-tat controversies with Republicans and instead focus on driving enrollment and promoting the benefits of the law.

If Republicans retake the Senate chamber and hold their House majority, Obama could spend his last two years in office vetoing legislation aimed at undermining or repealing the law.

Securing Success

Such fighting would hobble Obama’s ability to entrench his signature domestic achievement alongside now-sacrosanct entitlement programs such as Social Security, Medicare and President George W. Bush’s prescription drug benefit.

Obama already has suffered damage from the botched rollout. For the first time, 53 percent of Americans say he isn’t trustworthy or honest, according to a Nov. 25 CNN/ORC International survey.

The health-care law now has the “opportunity to realize the potential by end of March,” when the initial six-month open enrollment period ends, said David Plouffe, a former senior Obama adviser. Republicans’ “get-rid-of-Obamacare message is getting less effective by the day as more people sign up.”

Celebrity Endorsers

Next week, a number of celebrities will join in an effort organized by an independent group to boost enrollment on the online exchanges, said a person familiar with the plan, who wasn’t authorized to speak publicly about it. An advertising blitz will begin in January after the holiday season has ended, said the person.

Scarlett Johansson, Aisha Tyler, and Gabrielle Union have recorded phone messages that Planned Parenthood is using to promote enrollment. Actresses Lena Dunham of “Girls” and Elizabeth Banks of “Hunger Games” posted Twitter messages to promote a Planned Parenthood Internet town hall this week on Obamacare.

In addition, Planned Parenthood, which provides health services to women, will “ramp up significantly” its efforts to promote enrollment in January, deploying hundreds of staff members with a goal of contacting a half-million people in Texas, Florida, Ohio and Pennsylvania, said Rachel Fleischer, spokesperson for Planned Parenthood Federation of America.

Nationwide Events

Enroll America, an advocacy group with close ties to the White House, plans more than a thousand events across the country to promote coverage during the first three weeks of December, a 40 percent increase from the same period in November, said Justin Nisly, a spokesman.

The Democratic Congressional Campaign Committee, the campaign arm of House Democrats, sent statements to the hometown news media of 60 Republican lawmakers who have previously voted to repeal Obamacare, criticizing them for benefits that would be eliminated.

As the Democrats attempted to change the momentum in the fight, Republicans focused on examples of people who will pay higher insurance premiums, with Boehner citing his own experience yesterday. The law dropped members of Congress from the group plan offered to federal employees, forcing them to buy individual insurance policies.

“The thought crossed my mind” of not signing up for insurance and paying a penalty, the Ohio Republican said.

Boehner’s coverage plan will almost double his premiums and about triple his copays, he told reporters. “I’m thrilled to death,” he said dryly.

Boehner’s Plan

A Boehner aide who insisted on anonymity said the speaker currently pays a monthly premium of $433 and an annual deductible of $700 under his congressional plan. He would have a monthly $802 premium and a deductible of $2,000 for an equivalent family plan offered on the District of Columbia insurance exchange. His office documented Boehner’s enrollment through photos and blog posts.

Unlike most employer-provided group plans, the Obamacare individual plans charge more for older beneficiaries and for smokers. Boehner is a 64-year-old smoker.

Republicans said they also will focus on how government subsidies on premiums are calculated and verified. The still-troubled back end of the Web site, as it is known, communicates with insurance companies providing coverage and other government agencies.

“If the provider side is not taken care of pretty quickly, that is going to be an enormous problem,” said Representative Michael C. Burgess, a Texas Republican.

Structural Problem

Burgess, an obstetrician, sees a structural flaw with the law. Doctors may be bumped from insurance plans or choose not to participate in others. People will lose their doctors, he said.

“How do you force your doctor into an insurance plan where the reimbursement is so crummy they don’t want to be there?” Burgess said in an interview. “By what law are you going to require a doctor to take a patient?”

Republicans say that by highlighting shortcomings in the law, they may be able to renew a push to delay the individual mandate to have insurance coverage, according to a leadership aide who insisted on anonymity discuss internal strategy.

Representative Keith Ellison, a Minnesota Democrat, said the Republican strategy is simply to sabotage the law.

Rollout Woes

“If you try to make it work, it’s going to work for people,” said Ellison, co-chairman of the Congressional Progressive Caucus. At the end of the day, with all of the rollout woes, “I’d rather be in the Democratic spot than the Republican spot because in a few months people are going to have health care who’ve never had it before,” he said.

The health law provides for tax subsidies to defray part of the premium cost for individuals earning as much as $46,000 a year and as much as $94,000 for a family of four.

More than 1 million visitors gave the Obamacare website another chance on Dec. 2, a day after the government said it had made software repairs that ensure the site is functional for most users. Insure Central Texas, a nonprofit helping people navigate the enrollment process, said the rehabilitation of the website is an improvement.

“We were able to get people through the entire process and had people complete the application and select a plan in one sitting” on those first two days of December, Elizabeth Colvin, the director of the program, said in a Dec. 4 phone interview. “That generally took maybe two or three times before Thanksgiving.”

Enrollment Pace

She agreed with Jeffrey Zients, Obama’s incoming chief economic adviser and a lead consultant on the website repairs, who said Dec. 1 that healthcare.gov was “night and day” better than when it debuted in October.

Colvin’s group, established by the Austin, Texas-based nonprofit Foundation Communities, enrolled 31 people in 2 1/2 days this week, compared with 50 in October and November combined, she said.

Zients had technicians redesign the site’s “window shopping” feature, enabling people for the first time to browse plans available where they live and see prices based on their age as well as covered benefits, drugs, doctors and hospitals. That feature had attracted 790,000 people since the evening of Dec. 1, Julie Bataille, a spokeswoman for the Centers for Medicare and Medicaid Services, told reporters in a Dec. 4 conference call.

A “reset” feature was added to the site to let customers ditch applications if they encounter errors that halt their progress and start over, Bataille said.

Problems remain, particularly when information is transmitted to insurers. The companies have said data on their new customers is often incomplete or garbled.

Bataille said Dec. 2 that 80 percent of the errors were related to a single bug that caused Social Security numbers to be left off the form when it was transmitted. She hasn’t said how many of the transmissions have been made or how many contained errors.