WASHINGTON – The House on Friday approved a far-reaching elections and ethics bill – one that would change the way congressional elections are funded, impose new voter-access mandates on states, require “dark money” groups to publicize their donors and force disclosure of presidential candidates’ tax returns.

Democrats dubbed the bill H.R. 1, a designation meant to signal its place as a centerpiece of their congressional agenda. The measure, which has more than 500 pages, contains dozens of provisions favored by liberal advocacy groups, labor unions and other Democratic allies.

“It’s a power grab, a power grab on behalf of the people,” House Speaker Nancy Pelosi, D-Calif., said at an event staged on the Capitol steps ahead of the planned vote.

House Republicans sought to portray the legislation, which passed 234 to 193, as a federal government takeover that would undermine the integrity of elections.

The bill is headed for a brick wall in the Republican-controlled Senate, where Majority Leader Mitch McConnell, R-Ky., has dismissed it as the “Democrat Politician Protection Act” and made clear it will not get a vote. But Democrats and their allies believe passage of the bill Friday will build momentum for action in coming years if and when Democrats solidify control in Washington.

“If Mitch McConnell is the immovable object, H.R. 1 is the unstoppable force,” said Rep. John Sarbanes, D-Md., the lead author of the bill. “We’ll keep pushing on it.”

A central provision establishes public financing for congressional elections, giving candidates as much as a 6-1 match for small donations to participating campaigns. Republicans have attacked the measure for funneling taxpayer money to political candidates; Democrats reworked the bill to tap fine revenue from people and companies found guilty of corporate malfeasance.

Another key campaign finance provision would require nonprofit “dark money” groups that engage in political activity to disclose their large donors – a provision that has generated opposition from the American Civil Liberties Union and other advocacy groups who argue that disclosure could chill free speech.

The bill also aims to end partisan gerrymandering of congressional district by requiring independent state commissions instead of legislatures to draw lines. It would also create an automatic voter registration system, bar states from disenfranchising felons who have completed their sentences, create stricter rules surrounding voter-roll purges and weaken state laws requiring voters to present photo identification.

Other provisions include a requirement that presidential and vice-presidential candidates disclose 10 years of past tax returns, a mandatory new ethical code for the Supreme Court, an end to most first-class travel for federal officeholders and a provision making Election Day a national holiday.

McConnell called that last proposal a Democratic “power grab” earlier this year in one of several Senate floor speeches in which he has attacked various provisions of the bill as unnecessary, unconstitutional or unfair.

“This new House Democrat majority’s top priority is apparently assigning themselves an unprecedented level of control over how they get elected to Washington D.C., along with how, where, and what American citizens are allowed to say about it,” he said Tuesday. “More than anything else, Washington Democrats want a tighter grip on political debate and the operation of elections, nationwide.”

But Democrats insisted this week they are interested in good government, not amassing power.

“We must reject the culture of corruption here and put the power back in the hands of the people we represent,” Rep. Ann Kirkpatrick, D-Ariz., said during remarks on the House floor on Thursday. “We can clean up the muddy swamp behaviors by passing H.R. 1.”

The Washington Post’s John Wagner contributed to this report.