WASHINGTON — With the fate of hundreds of thousands of young, undocumented immigrants in the balance, the Senate on Monday will begin an open-ended debate on immigration — an exceedingly rare step that, in effect, will allow senators to attempt to build a bill from scratch on the Senate floor.
The highly unusual debate will test whether a series of legislative concepts and proposals championed by President Trump and a variety of Republicans and Democrats can garner 60 votes, the threshold for a measure to pass the Senate. No one has any idea how it will turn out.
“Whoever gets to 60 wins,” Senator Mitch McConnell, the Republican leader, told reporters last week. “And it will be an opportunity for 1,000 flowers to bloom.”
Mr. McConnell has scheduled a procedural vote for 5:30 p.m. Monday on an unrelated measure that will serve as a shell for building an immigration bill. He has set aside this week for debate.
The push on immigration comes against the backdrop of a ticking clock, and months of congressional inaction.
About 690,000 young immigrants who were brought to the United States illegally as children are shielded from deportation under an Obama-era initiative known as the Deferred Action for Childhood Arrivals, or DACA. But Mr. Trump suspended the initiative in September and gave lawmakers until March 5 to come up with a replacement that would protect the young immigrants, known as Dreamers, after proposed legislation called the Development, Relief and Education for Alien Minors, or DREAM Act.
Liberal interest groups and immigration rights activists have mobilized to insist on legal status for the Dreamers without the concessions demanded by the president and immigration hard-liners: billions for a southern border wall, an even more aggressive crackdown on illegal immigrants by Immigration and Customs Enforcement, or ICE, and dramatic changes to the legal immigration system that would favor skilled immigrants over the family members of citizens and green-card holders.
“As the Senate is poised to start debate on the humanitarian crisis Donald Trump caused when he cruelly ended DACA, here’s what every sitting Senator should remember: Americans want the Dream Act — not cruel deals that go against basic American values,” said Corinne Ball, campaign director for MoveOn.org, a liberal activist group. “Bargaining with Dreamers’ lives, attempting to trade their ability to work and live freely in the country they call home, and further emboldening ICE to terrorize their communities and break up families is an unacceptable and immoral compromise.”
As the debate begins, conservatives and anti-immigration groups are likely to be just as vociferous.
In such a polarized environment, there is a significant chance that the Senate will pass nothing by the end of the week — or that whatever measure the Senate does adopt will be thwarted by the House.
“We’re going to have something in the Senate that we haven’t had in a while,” Senator Jeff Flake, Republican of Arizona, said Sunday on the NBC program “Meet the Press.” “It’s a real debate on an issue where we really don’t know what the outcome is going to be.”
The negotiations to do so are complicated by Republicans’ demands to pair any protection for DACA recipients with an increase in border security, and other limits on legal immigration, and by conflicting pronouncements from Mr. Trump.
After telling lawmakers last month that he would sign whatever they sent him, Mr. Trump now insists that any proposal address what the White House is calling “four pillars”: protection for DACA recipients; an end to so-called “chain migration,” in which legal immigrants can sponsor their family members; an end to the diversity visa lottery, which is aimed at bringing in immigrants from underrepresented countries; and full funding for Mr. Trump’s proposed border wall, estimated to cost $25 billion over 10 years.
The White House recently put forth its own proposal, one that will almost certainly be offered as an amendment during the Senate debate. Several other proposals are floating around Capitol Hill, but so far none has garnered the backing of the White House. A bipartisan group calling itself the Common Sense Coalition, led by Senators Susan Collins, Republican of Maine, and Joe Manchin, Democrat of West Virginia, has been working on its own measure but has not released a plan.
At the same time, the idea of an open-ended debate is so novel that many newer senators say they have never experienced one, and are scurrying to learn the rules.
“For a lot of us, we’re going to have to learn this process,” said Senator Mike Rounds, Republican of South Dakota, who was elected in 2014.
Immigrant rights groups are nervous, and don’t know quite what to expect. Frank Sharry, executive director of America’s Voice, an immigrants’ rights group, put it this way: “This is going to be an uncertain, wild week.’’