Leading conservative Republicans from the House and Senate say Congress is moving too slowly on efforts to “repeal and replace” the Affordable Care Act. But their potential resistance to compromise — even with other members of their own party — underscores just how hard a task Republicans have set for themselves.

When four of the country’s five largest for-profit health insurers announced two summers ago that they would pair off, many saw the moves as a game changer. Now, with both the Aetna-Humana and Anthem-Cigna deals struck down by the federal courts, the implications for both the health insurance industry and antitrust enforcement are just as powerful. Here’s what the experts say about what those decisions mean, and what the future could hold.

President Trump’s secretary of health and human services, Tom Price, took office on Friday with a promise to fix what he called a “broken health care system” that was “harming Americans and their families.” Mr. Price was sworn in by Vice President Mike Pence just hours after the Senate, by a party-line vote of 52 to 47, confirmed his nomination in the early hours of Friday morning.

More than 12.2 million people have signed up for coverage nationwide this year under the Obama-era health care law even with the uncertainty created by President Donald Trump's vow to repeal and replace it.

In a surprise move Monday, Marathon Pharmaceuticals told patient advocates that it would “pause” the launch of its drug Emflaza because of pricing concerns expressed by patients and advocacy groups.

The number of Californians newly signed up for health insurance through Covered California, the state’s insurance marketplace created under the Affordable Care Act, dropped 3 percent compared with last year, according to enrollment figures released by Covered California on Monday.