The US Senate voted to take up a $1.9 trillion pandemic relief bill backed by President Joe Biden, setting off a lengthy and partisan debate expected to end this weekend with approval of the nation’s sixth stimulus since the pandemic-triggered lockdowns that began a year ago.

The 51-50 vote Thursday, with Vice President Kamala Harris providing the tie-breaker, reflected the solid opposition of Senate Republicans, who say the drive by Democrats to pass it on their own has resulted in a far-too-costly measure that will further boost US debt and could spark inflation.

The vote has the Senate considering a bill passed in the House a week ago, but the chamber will later vote on a package of changes offered by Senate Majority Leader Chuck Schumer that are designed to shore up support among Democrats. That includes tighter eligibility for $1,400 stimulus checks and subsidies for health insurance premiums of laid-off workers through September.

A host of other changes could come later in a debate that Republicans are threatening to stretch out for several days and that will end in a gruelling “vote-a-rama,” when senators can offer scores of amendments with rapid-fire debate and votes. In a chamber divided 50-50 between the two parties, with Harris able to break any ties, Democrats will be challenged to stay unified over votes that could politically risky or that could fundamentally alter the legislation.

As an added hurdle, GOP Senator Ron Johnson of Wisconsin is demanding an entire reading of the 700-page bill -- something that could take 10 hours. After that, the Senate will have as many as 20 hours of debate on the relief package. Then comes the vote-a-rama, which has no set endpoint under Senate rules. Democratic leaders have the ability to conclude at some point by declaring that Republicans are engaging in “dilatory” tactics.

“No matter how long it takes, the Senate is going to stay in session to finish the bill this week,” Schumer said on the Senate floor. “The American people deserve nothing less.”

The Senate is ploughing ahead despite warnings from federal law enforcement agencies that a militia group may be plotting to attack the Capitol on Thursday, about two months after a Jan. 6 siege of the building by extremist supporters of then-President Donald Trump that led to five deaths.

The House, which passed its own version of the relief bill on a 219-212 tally on Feb. 27, cancelled Thursday’s session and scaled back other events at least in part because of the threat. Democrats are racing the clock to get the stimulus legislation to Biden’s desk by March 14, when existing supplemental unemployment aid expires.

Both the House-passed bill and the version Schumer proposes would provide $1,400 stimulus checks, enhanced jobless benefits and funding for vaccines and testing. A boost in the nation’s minimum wage to $15 an hour that is in the House bill was removed in the Senate because it didn’t comply with Senate rules that Democrats are using to pass their bill with a simple majority of votes.

As part of the effort to keep Democrats together, the president agreed Tuesday to lower the income threshold for phasing-out stimulus payments in the aid bill, according to a Democratic aide.

Democratic Senators, including Joe Manchin of West Virginia and Jeanne Shaheen of New Hampshire, had advocated tighter eligibility to reduce funds being transferred to those who don’t need it. Their votes will be critical in passing the legislation.

Phase-Out

The payments begin phasing out above $75,000 in annual income for individuals and $150,000 for couples, the same as set in the House bill, the aide said on condition of anonymity. But under the Biden-backed Senate Democratic compromise, payments would fully phase out for individuals making more than $80,000, compared with a $100,000 cap in the House-passed bill. And the full phase-out for couples would be $160,000 instead of $200,000.

Asked at the White House Thursday whether he was comfortable with the limits on direct payments, Biden answered, “Yes.”

A separate push by moderates to trim supplemental unemployment benefits to $300-a-week from the $400 approved in the House won’t be included in what is initially brought to the Senate floor, according to the aide.

The Senate’s so-called managers’ amendment to the House bill is expected to keep the House’s figure, which is a $100-a-week increase from the current level, through August. However, that could still get cut back to $300 in the amendment process.

Other changes from the House bill were hammered out among Senate Democrats late Tuesday.

Insurance

One would subsidize 100% of the costs of continuing employer-based health insurance premiums through September for laid-off workers. The House bill would subsidize 85% of premiums for individuals eligible for so-called COBRA coverage in employer health plans.

Separately, the Senate bill would postpone by a year a provision in the House bill that lets states claw back money from drugmakers. The Senate’s version would end the cap on Medicaid’s drug rebate program in 2024 rather than in 2023, according to two people briefed on the Senate version. Democrats have proposed ending the drug-rebate caps, but hospitals and drug companies are among those who are pushing back.

Democratic Senator Debbie Stabenow of Michigan, a member of Schumer’s leadership team, said the various compromises will help usher the broad bill through the chamber.

“We’re in a good spot to get this done,” she said.

Senator Maria Cantwell of Washington, by contrast, said, “I think the package as it had been crafted was good to go.” She said that “I think people need money.”

Once the vote-a-rama starts the danger is that Republicans could reshape some of the provisions by peeling off just one Democrat.

GOP Senator Rob Portman of Ohio said Wednesday he’s working on amendments to further target the bill. Republican Senator Rick Scott of Florida said he’s planning many of his own, including one that would extend the Keystone XL oil pipeline after Biden revoked a key cross-border presidential permit for the Canadian-US project.

The Senate’s No. 2 Democrat, Dick Durbin of Illinois, predicted that Democrats would, in the end, stick together on the stimulus check and unemployment insurance language signed off on by Biden.

“I think some negotiations and concessions have been made to solidify the Democratic support,” Durbin said.

By Erik Wasson and Laura Litvan