John McCain and Russ Feingold used to be synonymous with their crusading overhaul of the campaign finance system that eliminated big money from federal elections.

But after a sea change to campaign finance laws following the Supreme Court “Citizens United” decision, McCain and Feingold are now benefiting from the largesse they once fought so fiercely against.

Supporters of Sen. McCain (R-Ariz.), seeking a sixth term after 30 years in the Senate, have boosted his campaign through a super PAC specifically designed to run ads on his behalf, financed almost entirely by six-figure donations from Wall Street titans and other corporate executives. Feingold, the former Senate Democrat trying to reclaim his old seat in Wisconsin, has been boosted by outside groups financed through “dark money” committees that don’t reveal their donors.

Neither is particularly happy about it, but they are not apologizing.

“Oh yeah, you’ve gotta play the game by the rules, but I don’t think there’s any doubt that there will be future scandals,” McCain said in an interview late last month after a campaign event outside Phoenix.

Feingold blames his opponent, Sen. Ron Johnson (R-Wis.), for declining to sign a “Badger Pledge” that would have likely forced all outside groups to stop spending money in the race. “Sen. Johnson refused to sign the Badger Pledge because he loves the corrupt campaign finance system the way it is,” Michael Tyler, Feingold’s spokesman, said.

The pair’s stance is perfectly understandable given today’s political climate. But it’s an amazing turn of events for the once loud champions of overhauling the campaign finance system.

By the mid-’90s, “soft money” had become a lightning rod in politics. Individual candidate for Congress and the presidency remained limited in what they could collect from individual donors and political action committees, but the Republican and Democratic campaign committees faced no limits in raking in campaign cash, and often raised checks in enormous amounts.

After collecting a few thousand dollars for their official campaign accounts, politicians could essentially tell wealthy donors to which party committee they could send an unlimited check for that candidate’s benefit.

The results were sometimes not pretty.

Bill Clinton’s 1996 presidential reelection bid ended up under congressional investigation over questions about whether foreign donors had improperly made soft money donations to the Democratic National Committee

Against that backdrop, McCain and Feingold — neither shy about rattling their party’s leadership — launched their crusade to eliminate soft money from elections. It took several years, but in 2001 and early 2002 Congress passed a final version of McCain-Feingold campaign finance reform and the landmark legislation took effect after the 2002 midterm elections.

“As long as the wealthiest Americans and richest organized interests can make the six and seven figure donations to political parties and gain the special access to power that such generosity confers on the donor, most Americans will dismiss the most virtuous politician’s claim of patriotism,” McCain said in March 2001 during Senate debate.

Under McCain-Feingold, donations to national party committees were limited to $25,000 (indexed for inflation), essentially removing the biggest donations from federal races. Some outside groups, such as the U.S. Chamber of Commerce and environmental groups, still aired ads during election season but they had to be vaguely worded and clearly connected to a policy issue before Congress.

McCain and Feingold’s biggest opponent, Sen. Mitch McConnell (R-Ky.), long before he became majority leader, dubbed their reform an “awful bill” and began the early legal challenges to it. Those challenges culminated in the Supreme Court’s 2010 “Citizens United” ruling that gutted McCain-Feingold, but did not restore soft money donations to party committees.

Instead, the ruling created an entirely new world of “super PACs,” outside groups that could accept unlimited donations from donors who sometimes don’t have to disclose their identities. The new system gave individual donors massive power and essentially created shadow campaigns for presidential and congressional candidates.

Former chiefs of staff to McConnell and Senate Minority Leader Harry M. Reid (D-Nev.) effectively run two major super PACs broadly benefiting Republicans and Democratic candidates, respectively.

One-by-one, candidates for the House and Senate have set up their own super PACs, rather than relying on Washington strategists at party committees to do it for them. That trend culminated this year with McCain and Feingold’s Senate campaigns.

Former McCain advisers established Arizona Grassroots Action, a super PAC that is neither from Arizona nor does it rely much on the grassroots.

Based in Alexandria, the PAC spent more than $2.1 million through mid-August, including $1.5 million in ads that were largely designed to paint McCain’s Republican primary challenger as out of touch.

Six donors have given at least $100,000 to the group, federal records show, including $350,000 from Ronald O. Perelman, the Manhattan billionaire whose holdings include Revlon; $100,000 from Paul Singer, the Wall Street hedge fund manager; and $200,000 from Access Industries, a New York holding company run by a Russian-born billionaire.

Feingold is the beneficiary of different interest groups, particularly environmental and abortion rights groups. While there is no super PAC dedicated solely to Feingold’s race, the League of Conservation Voters has spent almost $500,000 on his behalf, according to Democratic estimates.

Republicans contend that nearly $2 million from outside groups, such as Planned Parenthood, was spent against Johnson in 2015 alone.

To be sure, Johnson’s conservative allies have dwarfed the spending by liberal groups. Several groups connected to the Koch brothers have already spent $5 million trying to boost the former plastics manufacturer’s rematch against Feingold.

Feingold has made several proposals to reform the campaign finances system, but first he has to get elected. One area of focus might be forcing disclosure of all political donations, doing away with so-called dark money.

McCain, who is supporting Johnson’s re-election, said he would work with Feingold on the issue if the timing were right.

“There’s gotta be some kind of catalyst,” he said last month. “Right now all the politicians are happy with a super PAC and the status quo and all that, but there will be a scandal. That’s history, and it does repeat itself.”

Back in 2001, as McCain finished the debate on his bill, he called Feingold “a man of great courage and conviction. His partnership in this effort is one of the greatest privileges I have ever had in public life.”

That partnership might have a second act.