You’d think Biden and the Democratic party leadership would do everything in their power to stop Republicans from undermining democracy.

So far this year, the Republican party has passed roughly 30 laws in states across the country that will make voting harder, especially in Black and Latino communities. With Trump’s baseless claim that the 2020 election was stolen, Republicans are stoking white people’s fears that a growing non-white population is usurping their dominance.

Yet while Biden and Democratic leaders are openly negotiating with holdout senators for Biden’s stimulus and infrastructure proposals, they aren’t exerting similar pressure when it comes to voting rights and elections. In fact, Biden now says he won’t take on the filibuster, which stands firmly in the way.

What gives? Part of the explanation, I think, lies with an outside group that has almost as much influence on the Democratic party as on the Republican, and which isn’t particularly enthusiastic about election reform: the moneyed interests bankrolling both parties.

A more robust democracy would make it harder for the wealthy to keep their taxes low and profits high. So at the same time white supremacists have been whipping up white fears about non-whites usurping their dominance, America’s wealthy have been spending vast sums on campaign donations and lobbyists to prevent a majority from usurping their money.

They’re now whipping up resistance among congressional Democrats to Biden’s plan to tax capital gains at 39.6% – up from 20% – for those earning more than $1m, and they’re on the way to restoring the federal tax deduction for state and local taxes, of which they’re the biggest beneficiaries.

In recent years these wealth supremacists, as they might be called, have quietly joined white supremacists to become a powerful anti-democracy coalition. Some have backed white supremacist’s efforts to divide poor and working-class whites from poor and working-class Black and brown people, so they don’t look upward and see where most of the economic gains have been going and don’t join together to demand a fair share of those gains.

Similarly, white supremacists have quietly depended on wealth supremacists to donate to lawmakers who limit voting rights, so people of color continue to be second-class citizens. It’s no accident that six months after the insurrection, dozens of giant corporations that promised not to fund members of Congress who refused to certify Biden as president are now back funding them and their anti-voting rights agenda.

Donald Trump was put into office by this anti-democracy coalition. According to Forbes, 9% of America’s billionaires, together worth a combined $210bn, pitched in to cover the costs of Trump’s 2020 campaign. During his presidency Trump gave both parts of the coalition what they wanted most: tax cuts and regulatory rollbacks for the wealth supremacists; legitimacy for the white supremacists.

The coalition is now the core of the Republican party, which stands for little more than voter suppression based on Trump’s big lie that the 2020 election was stolen, and tax cuts for the wealthy and their corporations.

Meanwhile, as wealth supremacists have accumulated a larger share of the nation’s income and wealth than at any time in more than a century, they’ve used a portion of that wealth to bribe lawmakers not to raise their taxes. It was recently reported that several American billionaires have paid only minimal or no federal income tax at all.

Tragically, the supreme court is supporting both the white supremacists and wealth supremacists. Since Chief Justice John Roberts and Justice Samuel Alito joined in 2005 and 2006, respectively, the court has been whittling away voting rights while enlarging the rights of the wealthy to shower money on lawmakers. The conservative majority has been literally making it easier to buy elections and harder to vote in them.

The Democrats’ proposed For the People Act admirably takes on both parts of the coalition. It sets minimum national standards for voting, and it seeks to get big money out of politics through public financing of election campaigns.

Yet this comprehensiveness may explain why the Act is now stalled in the Senate. Biden and Democratic leaders are firmly against white supremacists but are not impervious to the wishes of wealth supremacists. After all, to win elections they need likely Democrats to vote but also need big money to finance their campaigns.

Some progressives have suggested a carve-out to the filibuster solely for voting rights. This might constrain the white supremacists but would do nothing to protect American democracy from the wealth supremacists.

If democracy is to be preserved, both parts of the anti-democracy coalition must be stopped.

• Robert Reich, a former US secretary of labor, is professor of public policy at the University of California at Berkeley and the author of Saving Capitalism: For the Many, Not the Few and The Common Good. His new book, The System: Who Rigged It, How We Fix It, is out now. He is a columnist for Guardian US