Donald Trump said that he had the right to choose a replacement for the late Supreme Court Justice Ruth Bader Ginsburg, while former Vice President Joe Biden alleged the president’s nominee would end health coverage for millions of people as they opened their first debate.

“We won the election,” Trump said in answer to the first question, about his nominee Amy Coney Barrett. “Elections have consequences. We have the Senate, we have the White House and we have a phenomenal nominee.”

Biden said that Trump and Barrett want to strike down the Affordable Care Act, costing 20 million people their health insurance.

“The American people have a right to have a say over who the Supreme Court nominee is,” Biden said. “What’s at stake here, as the president’s made it clear, he wants to get rid of the Affordable Care Act. He’s in the Supreme Court right now trying to get rid of the Affordable Care Act, which will strip 20 million people from having health insurance now, if it goes to the Supreme Court.”

The debate moderator, Fox News host Chris Wallace, tried to intervene as the two candidates squabbled over their respective health policies, and Trump complained “I guess I’m debating you.”

Hours before the debate began, Democratic nominee Joe Biden released his most recent tax returns, signaling that he wanted new revelations about the president’s taxes at center stage for their first face-to-face encounter.

The difference between the two candidates’ tax history is fodder for Biden’s argument that Trump has conned working-class voters into supporting him.

Biden paid nearly $300,000 in income taxes in 2019, according to his returns. Billionaire Trump, meanwhile, paid $750 in 2016 and 2017, and nothing in ten of the last 15 years, according to the New York Times.

The former vice president has sought in recent weeks to portray Trump as catering to the wealthy and well connected, as Biden tries to emphasize his working-class roots and promote an economic agenda he says would focus on the middle class.

The Times reporting on Trump’s taxes — information the president has insisted on keeping secret from voters — “reinforces what we already knew about Donald Trump, which is he looks down on working people, he views them as suckers, he thinks he’s smart because he doesn’t pay taxes,” Biden’s deputy campaign manager, Kate Bedingfield, said on a conference call with reporters before the debate.

However, the report is unlikely to cost Trump many votes. He was elected in 2016 after boasting about paying little income tax but breaking with modern precedent by refusing to release his returns, and his core supporters have consistently shown little interest in the issue.

But polls show that about two-thirds of Americans believe that Trump should release his tax returns and that he hasn’t been entirely honest with the IRS.

Biden’s returns Tuesday showing that he paid a 31.7% income tax rate gives strength to his argument that he has more in common with the White, working class voters he needs to win back from Trump than the president himself — even if that rate was on income of $944,737.

Tuesday’s presidential debate, the first of three before the Nov. 3 election, is hosted by Case Western Reserve University and the Cleveland Clinic.

The topics, which were announced last week by the Commission on Presidential Debates, include a comparison of the Trump and Biden records, the Supreme Court, the coronavirus, the economy, racial tensions, the violence in U.S. cities and the integrity of the election itself.

With five weeks left until Election Day, polls show Biden leading Trump nationally and in key swing states. The Democrat’s campaign has approached the debate as a high-stakes moment when he could cement his advantage or see it begin to erode.

Biden, an experienced debater after previous presidential and vice presidential bids and 36 years in the Senate, has previewed an approach focused on what he considers Trump’s failures, including “criminal” mismanagement of the pandemic. He will also seek to portray a second Trump term as one that would cause irreparable harm to U.S. democracy.

For Trump, the debate is a critical opportunity to try to regain momentum after months of declining poll numbers.

Trump, never a stickler for presidential decorum, is likely to attack Biden in deeply personal terms, portraying him as doddering and senile and alleging that his son Hunter engaged in corruption in Ukraine and China by leveraging his father’s political position.

While debaters traditionally seek to raise expectations for their opponents, Trump and his allies have for weeks lowered the bar for Biden, 77, by arguing that he is mentally impaired and exhausted. Only recently have Trump surrogates begun to focus on Biden’s experience in the forum.

That strategy could backfire. The coronavirus has sharply restricted the candidates’ ability to campaign, though Trump has resumed large in-person rallies. The debate will be the first opportunity for many voters to see Biden on a stage since the Democratic convention and he might only have to hold his own for the showdown with Trump to be declared a success.

But for some Democrats, a single gaffe or missed opportunity to take a swipe at Trump is likely to be cause for worry. Trump and his supporters, meanwhile, are likely to declare victory no matter what.

One planned topic of the debate will be the battle around Trump’s nomination of Amy Coney Barrett to the Supreme Court as a replacement for Justice Ruth Bader Ginsburg, who died Sept. 18.

Barrett’s nomination was greeted with enthusiasm by social conservatives, and Republicans are planning to try to confirm her to the court before Election Day. But many Democrats, including Biden, assert that putting in place a new justice so close to the election violates precedent and that the next president should make the nomination.