WASHINGTON — President Obama mounted a spirited defense of health care reform Tuesday night, acknowledging repeated attacks on the law while his administration works to smooth over its shaky rollout.

The president, in his State of the Union address, gave his signature legislation considerably more priority this year than in his last three speeches to joint sessions of the Congress. He spoke at length about the merits of recognizing pre-existing conditions for coverage purposes and of ensuring that all Americans have health insurance to provide “the peace of mind that if misfortune strikes, you don’t have to lose everything.”

“Because of this law, no American can ever again be dropped or denied coverage for a pre-existing condition like asthma, back pain or cancer,” he said. “No woman can ever be charged more just because she’s a woman.”

Last year Obama mentioned the Affordable Care Act and Medicare reform in general terms, and in 2012 the issue yielded one sentence. In 2011, he spoke briefly about the importance of requiring providers to accept subscribers with pre-existing conditions.

Health care represents one of the most contentious partisan issues in the 2014 election year, with Republicans exercising every opportunity to attack the law. About a dozen Republican lawmakers brought guests to the speech who they said have been negatively affected by the health care law.

Obama faced those attacks head on Tuesday night, chastising the GOP for “refighting old battles” and repeated efforts to repeal the Affordable Care Act – an on-going battle that fueled the partial government shutdown late last year. “Another forty-something votes” do not justify the law’s repeal, he said.

“When our differences shut down government or threaten the full faith and credit of the United States — then we are not doing right by the American people,” Obama said, receiving a standing ovation from many in the audience.

Most Republicans remained silent during the president’s remarks on health care, except when he acknowledged that he didn’t expect to convince opponents about the law’s merits. He invited them to “tell America what you’d do differently” and then “see if the numbers add up.”

“We all owe it to the American people to say what we’re for, not just what we’re against,” he said.

However, in his speech Obama avoided any mention of the bungled rollout of the insurance exchange website Healthcare.gov, which has been widely criticized for a host of technological glitches and poor user friendliness. Earlier this month the White House severed ties with CGI Federal, the site’s contractor, a move indicating the administration’s efforts to move forward from the exchange’s botched introduction.

Other aspects of Obama’s health care law have also been under fire, including its mandatory contraception coverage provisions. Hours before Obama’s speech, 15 Republican members of Congress filed Supreme Court amicus briefs arguing that the mandate violates religious freedoms. The justices will hear arguments on the case in March.

The president’s comments also come as the March 31 insurance sign-up deadline looms. Since the law went into effect, 6 million Americans have lost existing insurance coverage, while 3 million have signed up for plans through the new online exchange, according to administration officials. Obama encouraged Americans to make sure everyone they knew was covered by the deadline.

Although the legislation is meant to target young Americans, recently released statistics indicate the majority of those who have signed up for plans is middle-aged. About a quarter of those who have enrolled online are between 18 and 34 years old, the age range experts say is vital for making the new health care requirements advantageous for providers.