Senate Democrats on Tuesday proposed a pared-down voting rights bill that has the backing of both progressives and centrists in an effort to present a united front against deep Republican resistance to new legislation setting nationwide election standards.

The measure is the result of weeks of intraparty negotiations overseen by Senator Chuck Schumer, the New York Democrat and majority leader, and was built on principles put forward by Senator Joe Manchin III of West Virginia, the lone Democratic holdout against an earlier, much more sweeping piece of legislation called the For The People Act. Still, like that measure, it faces steep odds in the Senate, where it is unlikely to persuade Republicans to drop their opposition to legislation they have argued is an egregious overreach and an existential threat to their party.

The new bill, called the Freedom to Vote Act, drops some contentious elements of that initial bill such as restructuring the Federal Election Commission. It focuses heavily on guaranteeing access to the ballot following new voting restrictions being enacted around the country by Republican legislatures since the 2020 elections. And it would set a national voter identification standard — something that many Democrats have vehemently opposed — but one that would be far less onerous than some states have attempted to impose, allowing voters to meet the requirement with a variety of identification cards and documents in paper and digital form.

The revised measure would also require that states allow at minimum 15 consecutive days of early voting, including two weekends; ensure that all voters can request to vote by mail; establish new automatic voter registration programs, and make Election Day a national holiday. The legislation would mandate that states follow specific criteria when drawing new congressional districting lines and would force disclosure of donors to so-called dark money groups.

“Following the 2020 elections in which more Americans voted than ever before, we have seen unprecedented attacks on our democracy in states across the country,” said Senator Amy Klobuchar, the Minnesota Democrat who leads the Rules Committee, which is responsible for election oversight. “These attacks demand an immediate federal response.”

Mr. Manchin had balked at the original legislation and offered elements of a voting bill he would back, prompting the negotiations between him, Ms. Klobuchar and fellow Democratic Senators Jeff Merkley of Oregon, Tim Kaine of Virginia, Jon Tester of Montana, Alex Padilla of California and Raphael Warnock of Georgia. Senator Angus King, independent of Maine, also participated.

While Democrats cheered the new version, they also recognized that they were very unlikely to attract sufficient Republican support to break a filibuster against any voting bill, meaning that they would have to unite to force a change to Senate rules governing the filibuster if the legislation was to have any chance of passage. Republicans have already blocked debate on a voting rights measure twice before.

“We must be honest about the facts,” Mr. Schumer said Monday as he said he would try to break the impasse again next week. “The Republican-led war on democracy has only worsened in the last few weeks.”

Despite his support for the legislation, Mr. Manchin has reiterated multiple times his refusal to abolish the filibuster, though he has also indicated a willingness to entertain some changes. Mr. Schumer noted Monday that Mr. Manchin had been reaching out to Republicans to persuade them to back the new version of the voting rights bill.

Democrats hope continuing Republican opposition to a measure Mr. Manchin is now invested in as one of the chief authors will soften his opposition to weakening the filibuster, allowing his party to advance a measure they see as crucial to countering new voting restrictions in Republican-led states.

The proposal prompted an immediate call from progressive activists for Democrats to move forward on voting rights and not let the filibuster or Senator Mitch McConnell, the Kentucky Republican and minority leader, stand in the way.

“President Biden and Senate Democrats must now move quickly to address the filibuster and prevent Senator McConnell from abusing Senate rules to prevent this bill from getting a fair up-or-down vote,” the anti-filibuster group Fix Our Senate said in a statement.

Mr. Manchin did not mention the filibuster in a statement strongly endorsing the new proposal.

“The right to vote is fundamental to our democracy and the Freedom to Vote Act is a step in the right direction towards protecting that right for every American,” Mr. Manchin said. “As elected officials, we also have an obligation to restore peoples’ faith in our democracy, and I believe that the common sense provisions in this bill — like flexible voter ID requirements — will do just that.”