An explainer:

When the Senate voted 51-50 to begin debating the repeal of the Affordable Care Act, technically senators were bringing the repeal bill that was passed in the House to the Senate floor. For now, that is the bill that senators are trying to reshape.

On Tuesday night, Senate Republican leaders brought to the floor their most complete version of a plan to repeal and replace the Affordable Care Act. That measure had been worked out behind closed doors by the majority leader, Senator Mitch McConnell of Kentucky, and it would dismantle major parts of the current health care law, including the requirement that most people have health insurance.

But it also included an overture to Senate conservatives, a measure championed by Senator Ted Cruz, Republican of Texas, that would allow insurance companies to sell stripped down, low-cost insurance plans as long as they also offer insurance policies that comply with federal standards, including the requirement that plans cover essential services like maternity care, mental health treatment and prescription drugs.

Three major proposals are being discussed.

For moderates, the legislation includes $100 billion to help pay out-of-pocket medical costs for low-income people.

Because that broad version of the Senate health care measure had not yet been assessed by the nonpartisan Congressional Budget Office, it needed 60 votes to overcome a Democratic objection that it violated Senate rules.

But it got only 43 votes, demonstrating that even after weeks of refining the legislation, Senate leaders still fell far short of enough support for their replacement plan, from both ends of the partys ideological spectrum.

Mr. McCain had previously made clear that he wanted to secure amendments to that broad repeal-and-replace bill. The vote on Tuesday night could be interpreted as a sign of support for that general approach.

The debate goes on.

Senator John McCain, who was recently diagnosed with brain cancer, spoke to the Senate after casting his vote to begin debating legislation to repeal the Affordable Care Act.

Mr. Trump opened the day by attacking Ms. Murkowski.

But Mr. Trumps public shaming is not an effective strategy for Ms. Murkowski, who has dealt with worse from her party. In 2010, Ms. Murkowski retained her Senate seat in a historic win as a write-in candidate. She had lost Alaskas Republican primary that year to a Tea Party challenger and was largely abandoned by Republican leadership. Since then, she has not felt beholden to her party.

Senators are set to consider a different repeal measure on Wednesday.

This measure would repeal major parts of the health law but would not provide a replacement. The legislation resembles a bill that passed the Senate in 2015 but was vetoed by President Barack Obama in early 2016.

Senator Rand Paul, Republican of Kentucky, supports that approach. But some Republicans worry that repealing the law without providing a replacement would leave many Americans without health care coverage. Such a repeal only measure is not expected to garner enough votes for passage.

The vote for this measure had been expected to take place around midday Wednesday, but it has now been delayed until later in the afternoon.

Republicans are using special budget rules to try to pass a repeal bill, so the debate is limited to 20 hours, and Democrats cannot delay it with a filibuster. Later this week, the Senate will hold what is known as a vote-a-rama, an exhausting marathon of amendment votes.

The nine Republicans who voted against the comprehensive replacement measure on Tuesday night are an indication of the problem that Senate Republican leaders continue to confront: The party caucus still does not agree on what should be in a health care repeal bill that would have enough support to win Senate approval.

One solution might be to pass a pared-down health plan that has support from at least 50 of the 52 Republican senators, and then turn to working out a compromise with the House.

Read more:

Senate Health Care Vote: Where the Debate Left Off and What Happens Next - New York Times