Updated: June 24, 6:22 p.m.

House Democrats on Thursday narrowly eked out a majority for a campaign finance reform package tightening rules on political spending by outside groups.

The bill, called the DISCLOSE Act, passed 219-206 after Democratic leaders managed to convert enough holdout liberal and black lawmakers concerned with an exemption tailored for the National Rifle Association. Thirty-six Democrats voted against the package, and only two Republicans backed it.

Democratic leaders have made the package a priority as the midterm elections near, believing that a controversial Supreme Court decision in January lifting limits on outside spending would lead to a flood of hostile corporate money against the party. But its path forward in the Senate remains unclear, with Republican leaders in that chamber rallying opposition and some Democrats objecting to the NRA carve-out.

The depth of the antipathy toward the bill among a wide variety of House Democrats was laid bare earlier Thursday on the rule governing debate, which 34 rank-and-file Members opposed. The opposition comprised everyone from rural Blue Dog Democrats to black lawmakers from big cities.

The bill was also a top concern for the White House, whose lobbying arm leaned into the whip effort in the House this week. President Barack Obama caused a stir on the issue in his State of the Union address, in which he blasted the decision as the Supreme Court justices sat in front of him.

But Democrats from Obama’s hometown of Chicago were among the most resistant to the package. They cited the difficulty of stomaching the NRA exemption after an explosion of gun violence in the Windy City last weekend left at least 10 people dead and 44 wounded.

Rep. Luis Gutierrez (D-Ill.), for example, initially voted against final passage of the measure, only switching his vote after an extended conversation on the floor with Speaker Nancy Pelosi (D-Calif.). Two other Chicago Democrats — Reps. Danny Davis and Bobby Rush — could not be convinced.

The vote marked a major win for its author, Rep. Chris Van Hollen, who took an unusually prominent role in guiding it to passage. The Maryland Democrat — who serves in leadership as both chairman of the Democratic Congressional Campaign Committee and assistant to the Speaker — took his lumps along the way, enduring stinging behind-the-scenes criticisms from some moderates who felt he bungled its development.

They complained that they were being forced to vote on a bill that stirred rage among business groups without appearing to have a shot of clearing the Senate.

“We all know that campaign finance reform is always difficult. I mean, look at how long it took McCain-Feingold to get through,” Van Hollen said after the vote, referencing the landmark 2002 reform package. “For a piece of legislation that has an unprecedented degree of transparency, this moved actually at a pretty brisk pace.”

Republicans remained nearly united in opposition, slamming the measure as an outrageous and unconstitutional power grab by the majority — and an attempt to silence business while empowering their labor union allies. That charge got some last-minute fuel with the addition of a provision that Republicans say spares unions from many of the same reporting requirements business groups may soon face.

On Wednesday, House Administration Chairman Robert Brady (D-Pa.) inserted a provision that likely exempts organized labor from reporting transactions to the Federal Election Commission when dues payments are set aside for political activity.

According to the bill’s final language, organizations are not required to meet a proposed reporting requirement if the payments are “funds attributable to dues, fees or assessments which are paid by individuals on a regular, periodic basis in accordance with a per-individual calculation which is made on a regular basis.”

The libertarian Center for Competitive Politics called the provision “a glaring carve out for the benefit of labor unions” that would allow organized labor “to shift unlimited amounts of money through various local and federal entities and never have to report or disclose any of it, while many nonprofits and trade groups would.”

“The insider, backroom deals congressional leaders cut with the most powerful interest groups in Washington illustrate why the First Amendment was written to restrict government from regulating political speech,” Center for Competitive Politics President Sean Parnell said in a statement. “The DISCLOSE Act would carve up the First Amendment, doling out free speech rights to favored allies while restricting likely critics as midterm elections approach.”