Amid questioning about democracy and the Trump mob attack on the U.S. Capitol, Biden took a shot at Trump's historic conviction in the hush money case.

"The only convicted felon is the guy standing on the stage with me now," Biden said.

Trump then quickly brought up Hunter Biden's recent conviction on federal gun charges.

Trump largely avoiding taking on a question about what he would say to Americans who believe he violated his oath on Jan. 6, 2021, and are worried he would do it again.

Instead, he pivoted to the border and to criticizing Biden's record.

Moderator Jake Tapper pressed him again, saying there was 80 seconds remaining to answer the question. Trump went on to attack former House Speaker Nancy Pelosi.<

In a heated moment in response to Trump's claim that the president "doesn't care about our veterans," Biden referenced a 2020 Atlantic article in which Trump was reported to have called Americans killed as "suckers" while on a trip to visit the Aisne-Marne American Cemetery in France in 2018.

On the subsequently canceled visit, the Atlantic reported that Trump told senior staff members, "Why should I go to that cemetery? It’s filled with losers."

Referring to his late son Beau during the debate, Biden said to Trump, "My son was not a loser, was not a sucker. You're the sucker, you're the loser."

Trump responded by saying it was in a "third-rate magazine" and the source had "made it up."

During the debate, Trump claimed that Democrats "support abortion up to and even beyond the ninth month," and contended that some Democratic states have had such a stance.

Democrats have never advocated for killing a baby after it is born as this would be murder, which is illegal in every state. Nine states have no abortion restrictions in place; however, it should be noted that late-term abortions are exceedingly rare, representing 1%, according to KFF.

After tonight's debate, there will be a rush to anoint a "winner" and a "loser," but the only way we can really do that is once we have data on how the debate will actually affect people’s votes. To that end, 538 partnered with Ipsos to poll the same group of likely voters both before and after the debate to see how their attitudes change. Here are some of the key findings from our pre-debate poll, which was conducted using Ipsos' KnowledgePanel.

First, we asked respondents to rate how well they thought each candidate would perform in the debate tonight on a five-point scale. On average, Trump got a score of 2.96 out of 5, and Biden got a score of 2.58 out of 5. In other words, expectations are significantly lower for Biden tonight, which could end up helping him -- even a so-so performance from Biden would exceed most people's expectations.

It looks like the reason people have such low expectations for Biden is his advanced age. We also asked respondents to grade each candidate's physical, mental and emotional fitness on a five-point scale. On average, Biden got just a 2.3 out of 5 on physical fitness and a 2.4 out of 5 on mental fitness. Trump bested him on both of those measures, but Trump got only a 2.6 out of 5 on emotional fitness, which was lower than Biden's score.

We also asked voters what issues would have the most impact on their vote. Fifty percent ranked inflation or increasing costs as one of their top three issues, while 37% included immigration. Voters also said Trump would do a better job handling those issues than Biden, so it will be especially important for the president to show strength on these issues tonight.

Finally, we asked voters which candidates they were considering supporting. Heading into the debate, 44.8% of voters are at least considering voting for Trump, 44.5% are at least considering voting for Biden and 18.5% are at least considering voting for independent candidate Robert F. Kennedy Jr., who failed to qualify for the debate. (Respondents could say they were considering multiple candidates, which is why these numbers add up to more than 100%.) We'll ask voters the same question after the debate to see whether these numbers shift.

-538's Nathaniel Rakich