WASHINGTON — Within the nationwide wrestle over voting rights, Democrats have rested their hopes for turning again a wave of new restrictions in Republican-led states and increasing poll entry on their slender majorities in Congress. Failure, they’ve repeatedly insisted, “isn’t an possibility.”

However as Republican efforts to clamp down on voting prevail throughout the nation, the drive to enact probably the most sweeping elections overhaul in generations is faltering within the Senate. With a self-imposed Labor Day deadline for motion, Democrats are struggling to unite round a method to beat strong Republican opposition and an almost certain filibuster.

Republicans in Congress have dug in in opposition to the measure, with even probably the most average dismissing it as bloated and overly prescriptive. That leaves Democrats no possibility for passing it apart from to attempt to pressure the invoice by way of by destroying the filibuster rule — which requires 60 votes to place apart any senator’s objection — to go it on a easy majority, party-line vote.

But Senator Joe Manchin III of West Virginia, the Democrats’ decisive swing vote, has repeatedly pledged to protect the filibuster and is refusing to signal on to the voting rights bill. He calls the laws “too darn broad” and too partisan, regardless of endorsing such proposals in previous periods. Different Democrats additionally stay uneasy about a few of its core provisions.

In a speech on Tuesday, President Biden vowed to “combat like heck” to enact the measure, saying he would ask Vice President Kamala Harris to assist push it by way of.

“June ought to be a month of motion on Capitol Hill,” he mentioned as he commemorated the centennial of the Tulsa race massacre.

However Mr. Biden alluded to the steep obstacles to that motion in Congress, singling out Mr. Manchin and Senator Kyrsten Sinema of Arizona — a second Democrat who has pledged to not change the filibuster — with out naming them.

“I hear all the oldsters on TV saying, ‘Why doesn’t Biden get this carried out?’” the president mentioned. “Effectively, as a result of Biden solely has a majority of successfully 4 votes within the Home and a tie within the Senate, with two members of the Senate who vote extra with my Republican pals.”

Navigating the 800-page For the Individuals Act, or Senate Invoice 1, by way of an evenly cut up chamber was by no means going to be a straightforward activity, even after it passed the House with only Democratic votes. However the Democrats’ technique for transferring the measure more and more hinges on the longest of lengthy pictures: persuading Mr. Manchin and the opposite 49 Democrats to help each the invoice and the gutting of the filibuster.

“We ought to have the ability to go it — it actually can be transformative,” Senator Chris Coons, Democrat of Delaware, mentioned just lately. “But when we’ve a number of members of our caucus who’ve simply point-blank mentioned, ‘I can’t break the filibuster,’ then what are we even doing?”

Summarizing the occasion’s problem, one other Democratic senator who requested to stay nameless to debate technique summed it up this manner: The trail to passage is as slender as it’s rocky, however Democrats haven’t any alternative however to die making an attempt to get throughout.

The hand-wringing is more likely to solely intensify within the coming weeks. On Friday, Senator Chuck Schumer of New York, the bulk chief, vowed to pressure a ground debate in late June, testing Mr. Manchin’s opposition and laying the groundwork to justify scrapping the filibuster rule.

“Hopefully, we are able to get bipartisan help,” Mr. Schumer mentioned. “To this point, we’ve not seen any glimmers on S. 1, and if not, every part is on the desk.”

The stakes, each politically and for the nation’s elections, are monumental.

The invoice’s failure would enable the enactment of restrictive new voting measures in Republican-led states reminiscent of Georgia, Florida and Montana to take impact with out legislative problem. Democrats concern that might empower the Republican Social gathering to pursue a method of marginalizing Black and younger voters based mostly on former President Donald J. Trump’s false claims of election fraud.

If the measure handed, Democrats might successfully overpower the states by putting in new nationwide mandates that they arrange computerized voter registration, maintain common no-excuse early and mail-in voting, and restore the franchise to felons who’ve served their phrases. The laws would additionally finish partisan gerrymandering of congressional districts, restructure the Federal Election Fee and require tremendous PACs to reveal their large donors.

A legion of advocacy teams and civil rights veterans argue that the combat is simply beginning.

“This sport isn’t carried out — we’re simply gearing up for a ground combat,” mentioned Tiffany Muller, the president of Finish Residents United and Let America Vote, that are spending millions of dollars on television ads in states like West Virginia. “On the finish of the day, each single senator goes to have to choose if they will vote to uphold the fitting to vote or uphold an arcane Senate rule. That’s the scenario that creates the strain to behave.”

Proponents of the overhaul on and off Capitol Hill have targeted their consideration for weeks on Mr. Manchin, a centrist who has expressed deep considerations in regards to the penalties of pushing by way of voting laws with the help of just one occasion. To this point, they’ve taken a intentionally hands-off strategy, betting that the senator will understand that there is no such thing as a actual compromise available with Republicans.

There may be little signal that he has come to that conclusion on his personal. Democrats huddled final week in a big convention room atop a Senate workplace constructing to debate the invoice, ensuring Mr. Manchin was there for an elaborate presentation about why it was very important. Mr. Schumer invited Marc E. Elias, the well-known Democratic election lawyer, to elucidate intimately the extent of the restrictions being pushed by way of Republican statehouses across the nation. Senators as ideologically numerous as Raphael Warnock of Georgia, a progressive, and Jon Tester of Montana, a centrist, warned what may occur if the occasion didn’t act.

Mr. Manchin listened silently and emerged saying his place had not modified.

“I’m studying,” he advised reporters. “Mainly, we’re going to be speaking and negotiating, speaking and negotiating, and speaking and negotiating.”

Regardless of the extraordinary give attention to him, Mr. Manchin isn’t the one hurdle. Ms. Sinema is a co-sponsor of the election overhaul however has not budged on the filibuster. A handful of different Democrats have shied away from definitive statements however aren’t any much less hesitant to put off the rule.

“I’m to not that time but,” Mr. Tester mentioned. He additionally signaled he is likely to be extra snug modifying the invoice, saying he “wouldn’t lose any sleep” if Democrats dropped a provision that might create a brand new public marketing campaign financing system for congressional candidates. Republicans have pilloried it.

“Initially, we’ve to determine if we’ve all of the Democrats on board. Then we’ve to determine if we’ve any Republicans on board,” Mr. Tester mentioned. “Then we are able to reply that query.”

Republicans are hoping that by banding collectively, they’ll doom the measure’s prospects. They succeeded in deadlocking a key committee considering the legislation, although their opposition didn’t bar it from advancing to the total Senate.

They accuse Democrats of utilizing the voting rights provisions to distract from different provisions within the invoice, which they argue are designed to present Democrats lasting political benefits. If they’ll forestall Mr. Manchin and others from altering their minds on preserving the filibuster, they’ll have thwarted the whole endeavor.

“I don’t assume they’ll persuade 50 of their members that is the fitting factor to do,” mentioned Senator Roy Blunt, Republican of Missouri. “I feel it will be onerous to elucidate giving authorities cash to politicians, the partisan F.E.C.”

Within the meantime, Mr. Manchin is pushing the occasion to embrace what he sees as a extra palatable different: laws named after Consultant John Lewis of Georgia, the civil rights icon who died last year, that might restore a key provision of the Voting Rights Act of 1965 that the Supreme Court docket struck down in 2013.

That measure would revive a mandate that states and localities with patterns of discrimination clear election regulation modifications with the federal authorities prematurely.

In actuality, although, that invoice has no higher likelihood of changing into regulation with out eliminating the filibuster. For the reason that 2013 determination, when the justices requested Congress to ship them an up to date pre-clearance system for reinstatement, Republicans have proven little curiosity in doing so.

Just one, Senator Lisa Murkowski of Alaska, helps laws reinstating the voting rights provision within the Senate. Requested just lately in regards to the prospect of constructing extra Republican help, Ms. Murkowski identified that she had been unable to draw one other co-sponsor from her occasion within the six years because the invoice was first launched.

Complicating issues, it has but to really be reintroduced this time period and might not be for months. As a result of any new enforcement provision must go muster with the courts, Democrats are continuing cautiously with a sequence of public hearings.

All that has created an unlimited time crunch. Election legal professionals have suggested Democrats that they’ve till Labor Day to make modifications for the 2022 elections. Past that, they may simply lose management of the Home and Senate.

“The time clock for that is working out as we strategy a midterm election once we face dropping the Senate and even the Home,” mentioned Consultant Terri A. Sewell, a Democrat who represents the so-called Civil Rights Belt of Alabama and is the lead sponsor of the invoice named for Mr. Lewis.

“If the vote and defending the rights of all People to train that almost all treasured proper isn’t value overcoming a procedural filibuster,” she mentioned, “then what’s?”

Luke Broadwater contributed reporting.