An anti-tax group funded primarily by billionaires has emerged as one of the biggest backers of the Republican lawmakers who sought to overturn the US election results, according to an analysis by the Guardian. The Club for Growth has supported the campaigns of 42 of the rightwing Republicans senators and members of the House of Representatives who voted last week to challenge US election results, doling out an estimated $20m to directly and indirectly support their campaigns in 2018 and 2020, according to data compiled by the Center for Responsive Politics. About 30 of the Republican hardliners received more than $100,000 in indirect and direct support from the group. The Club for Growth’s biggest beneficiaries include Josh Hawley and Ted Cruz, the two Republican senators who led the effort to invalidate Joe Biden’s electoral victory, and the newly elected far-right gun-rights activist Lauren Boebert, a QAnon conspiracy theorist. Boebert was criticised last week for tweeting about the House speaker Nancy Pelosi’s location during the attack on the Capitol, even after lawmakers were told not to do so by police. Public records show the Club for Growth’s largest funders are the billionaire Richard Uihlein, the Republican co-founder of the Uline shipping supply company in Wisconsin, and Jeffrey Yass, the co-founder of Susquehanna International Group, an options trading group based in Philadelphia that also owns a sports betting company in Dublin. While Uihlein and Yass have kept a lower profile than other billionaire donors such as Michael Bloomberg and the late Sheldon Adelson, their backing of the Club for Growth has helped to transform the organization from one traditionally known as an anti-regulatory and anti-tax pro-business pressure group to one that backs some of the most radical and anti-democratic Republican lawmakers in Congress. “Here’s the thing about the hyper wealthy. They believe that their hyper-wealth grants them the ability to not be accountable. And that is not the case. If you’ve made billions of dollars, good on you. But that doesn’t make you any less accountable for funding anti-democratic or authoritarian candidates and movements,” said Reed Galen, a former Republican strategist who co-founded the Lincoln Project, the anti-Trump campaigners. Galen said he believed groups such as the Club for Growth now served to cater to Republican donors’ own personal agenda, and not what used to be considered “conservative principles”. The Lincoln Project has said it would devote resources to putting pressure not just on Hawley, which the group accused of committing sedition, but also on his donors. The Club for Growth has so far escaped scrutiny for its role supporting the anti-democratic Republicans because it does not primarily make direct contributions to candidates. Instead, it uses its funds to make “outside” spending decisions, like attacking a candidate’s opponents. In 2018, Club for Growth spent nearly $3m attacking the Democratic senator Claire McCaskill in Missouri, a race that was ultimately won by Hawley, the 41-year-old Yale law graduate with presidential ambitions who has amplified Donald Trump’s baseless lies about election fraud. That year, it also spent $1.2m to attack the Texas Democrat Beto O’Rourke, who challenged – and then narrowly lost – against Cruz. Other legislators supported by Club for Growth include Matt Rosendale, who this week called for the resignation of fellow Republican Liz Cheney after she said she would support impeachment of the president, and Lance Gooden, who accused Pelosi of being just as responsible for last week’s riot as Trump. Dozens of the Republicans supported by Club for Growth voted to challenge the election results even after insurrectionist stormed the Capitol, which led to five deaths, including the murder of a police officer. The Club for Growth has changed markedly as the group’s leadership has changed hands. The Republican senator Pat Toomey, who used to lead the group, has recently suggested he was open to considering voting for Trump’s impeachment, and criticised colleagues for disputing election results. Its current head, David McIntosh, is a former Republican member of Congress who accompanied Trump on a final trip to Georgia last week, the night before Republican candidates David Perdue and Kelly Loeffler, both heavily supported by the Club for Growth, lost runoff elections to their Democratic opponents. Neither the Club for Growth nor McIntosh responded to requests for comment. Public records show that Richard Uihlein, whose family founded Schlitz beer, donated $27m to the Club for Growth in 2020, and $6.7m in 2018. Uihlein and his wife, Liz, have been called “the most powerful conservative couple you’ve never heard of” by the New York Times. Richard Uihlein, the New York Times said, was known for underwriting “firebrand anti-establishment” candidates like Roy Moore, who Uihlein supported in a Senate race even after it was alleged he had sexually abused underage girls. Moore denied the allegations. A spokesman for the Uihleins declined to comment. Yass of Susquehanna International, who is listed on public documents as having donated $20.7m to the Club for Growth in 2020 and $3.8m in 2018, also declined to comment. Yass is one of six founders of Susquehanna, called a “crucial engine of the $5tn global exchange-traded fund market” in a 2018 Bloomberg News profile. The company was grounded on the basis of the six founders mutual love of poker and the notion that training for “probability-based” decisions could be useful in trading markets. Susquehanna’s Dublin-based company, Nellie Analytics, wages on sports. In a 2020 conference on the business of sports betting, Yass said sports betting was a $250bn industry globally, but that with “help” from legislators, it could become a trillion-dollar industry. A 2009 profile of Yass in Philadelphia magazine described how secrecy pervades Susquehanna, and that people who know the company say “stealth” is a word often used to describe its modus operandi. The article suggested Yass was largely silent about his company because he does not like to share what he does and how, and that those who know him believe he is “very nervous” about his own security. Yass, who is described in some media accounts as a libertarian, also donated to the Protect America Pac, an organisation affiliated with Republican senator Rand Paul. The Pac’s website falsely claims that Democrats stole the 2020 election.