President Biden and Democratic lawmakers will face many challenges this year as they attempt to dramatically redirect policy after four years of Donald Trump’s presidency. None will be as consequential for the future of elections and the shape of democracy as the coming battle in the Senate over a comprehensive election revision bill.

In its simplest description, the legislation is designed to make it easier for people to vote, make elections more transparent and shore up some of the infrastructure of election operations. Such a description, however, belies the breadth of what is included in the nearly 800-page bill, which carries the biggest proposed changes for elections in decades.

The contents cover major changes to campaign finance law, including rules to expose dark-money contributions and the creation of a small-donor federal matching system for House elections. The bill would shift control over how congressional districts are drawn, taking power from politicians and giving it to independent commissions, as some states already have done. The bill also would tighten ethics and lobbying rules, deal with foreign interference in elections and set a code of conduct for federal judges.

The proposed changes to how people vote touch on many of the issues that became flash points in the 2020 election. The bill would provide for automatic voter registration, require use of paper ballots, allow no-excuse mail-in voting, set standards for the number of days for early in-person voting and require states to begin processing mail-in ballots well ahead of Election Day to lessen post-election counting controversies.

Two years ago, the Democratic-controlled House approved H.R. 1 on a party-line vote, with every expectation that the legislation would die in the Republican-controlled Senate, as it did. Last week, House Democrats pushed through this year’s version of H.R. 1, again along strict party lines. The bill’s future is brighter this year due to Democratic control of the Senate, but passing it will be a monumental task, a battle that could be decided by whether Democrats are prepared — or able — to end the filibuster.

The bill, labeled S.1 to show its priority status, now sits in the Rules and Administration Committee, chaired by Sen. Amy Klobuchar (D-Minn.). The committee members include Senate Majority Leader Charles E. Schumer (D-N.Y.) and Senate Minority Leader Mitch McConnell (R-Ky.). The first hearing is set March 24. Klobuchar said she hopes to start marking up the measure sometime in April, with the prospect for floor action later this spring.

Klobuchar noted many of the provisions in the omnibus bill are individual pieces of legislation that were introduced in the past with bipartisan sponsorship — among them bills she co-sponsored with Republicans. Some are similar to measures that have been approved in many states, including states with Republican governors or Republican legislatures. Some provisions would force blue states in the Northeast with antiquated rules to shape up their procedures.

“Not all provisions are bipartisan but a lot are,” Klobuchar said.

That carries little weight with Republicans. They see the legislation as a vast overreach by the federal government into the affairs of the states, although after many GOP lawmakers supported an effort to get the Supreme Court to overturn election results in several states, that argument is less persuasive. Mostly they see it as a partisan exercise by the Democrats to tip the scales in their favor in future elections.

Republicans have attacked the measure with extravagant language, highlighted by what former vice president Mike Pence recently wrote in the Daily Signal. Pence said the bill “would increase opportunities for election fraud, trample the First Amendment, further erode confidence in our elections and forever dilute the votes of legally qualified eligible voters.” He said the measure’s sole goal is “to give leftists a permanent, unfair and unconstitutional advantage in our political system.”

Pence prefaced this attack by claiming that there were “significant voting irregularities” in the 2020 election, when in fact there were not “significant” irregularities and nothing on the scale that would have changed the results of the presidential race. Pence’s language gives credence to the false assertion advanced by Trump and supported by many other Republicans that the election was rigged and stolen, again in the absence of credible evidence to prove it.

Ben Ginsberg, a Republican election-law attorney who called out Trump’s falsehoods about the election being stolen, said that in any bill this big, there are good provisions and questionable ones. “It’s an almost 800-page bill, so while there is some fine stuff in there, significant other parts read like a bill hijacked by the wily political operatives in the Democratic Party. . . . It’s a huge gift to the Republicans because two weeks ago the story was GOP civil war and now, lo and behold, they’re unified.”

The debate in Congress over the For the People Act is set against the backdrop of action by Republican legislators in states to make voting more difficult. According to the Brennan Center for Justice, which has pushed for the federal legislation, about 250 bills to restrict voting have been introduced or pre-filed in 43 states, a roughly sevenfold increase over a year ago. Many of these state-level bills would tighten rules for mail-in ballots or require more restrictive voter identification provisions.

“Democrats and Republicans have very different views on how to run elections, on how easy it should be to vote,” said Nate Persily, a professor at Stanford Law School, an expert on election laws and procedures, and an advocate for H.R. 1. “They have diametrically opposed views on how elections should be financed and how districts should be drawn. There is very little middle ground here. If Democrats had 60 votes in Senate, it would be a different battle, but it is their last chance to make some of these changes in time for the 2024 election.”

Michael Waldman, president of the Brennan Center, said the combination of new facts and new momentum have helped to push the federal legislation forward, though he acknowledged significant obstacles remain. “In the states, legislatures are rushing to enact restrictive voting laws, the most significant since the Jim Crow era,” he said. “Congress has the power to stop that cold, legally and constitutionally, and what it needs is the political will.”

Given the 50-50 split in the Senate, the federal legislation will go nowhere unless Democrats are united on the contents — no small issue. “We are doing very well with Democratic support,” Klobuchar said, while noting that she is working hard to unite her party behind the bill.

The window for action is limited, and because of Republican opposition, Democrats will likely have to decide whether getting rid of the filibuster is the only avenue to enactment. “One can view the fight over H.R. 1 as a lens through which to view our politics right now,” Persily said. “The Democrats at some point were going to have to decide whether they would use the ‘nuclear option’ [of eliminating the filibuster] and whether reforming democracy is the battlefield on which they want to have that fight. It’s not clear that they are going to be able to pass any substantial legislation without elimination of the filibuster.”

Klobuchar favors getting rid of the filibuster entirely, as do a growing number of Democrats beyond the party’s liberal wing. “It is not that I am not bipartisan,” she said. “I have a record of working across the aisle. . . . I still think that, if we’re going to act, we can’t wait anymore on things like immigration, climate change legislation — and significantly on this bill.”

Biden’s ambitious agenda could depend on whether Democrats are able to change the rules. Election revision could be the vehicle that answers that question.