President Biden and former President Donald Trump clashed repeatedly Thursday night in their first debate of the 2024 presidential election.

The candidates sparred over numerous topics, including the economy, abortion, immigration, and health care costs.

Hosted by CNN at the network’s studios in Atlanta, the debate featured a new set of rules: there was no studio audience, the candidates’ microphones were muted when their opponent spoke, no prewritten notes were allowed, and neither candidate presented opening statements. Trump had the final word during closing statements, as determined by a coin flip.

Nevertheless, the rhetoric got heated at times. Biden at one point referred to Trump as a “felon,” a reference to his recent 34 guilty counts in a hush money trial. Trump called Biden “Brandon,” a derogatory nickname his followers have adopted for the president. The two called each other the worst president in the history of the country.

Biden spoke haltingly at times and his voice was hoarse, which his campaign attributed to a cold. His performance caused immediate concern among the Democratic ranks.

The presidential debate happened unusually early, more than four months before voters head to the polls on November 5. This event marked the first significant face-off between the two main candidates. Highlighting the early timing of Thursday’s debate, neither Trump nor Biden has officially secured their party’s nominations yet, which will be confirmed at their respective conventions later this summer.

Biden, 81, and Trump, 78, have been neck and neck in polls throughout the year. A recent Yahoo News/YouGov poll indicated Biden holding a slim lead over Trump, 46% to 44%. Only these two frontrunners took the stage Thursday night, as independent and third-party candidates Robert F. Kennedy Jr., Jill Stein, and Cornel West did not qualify.

Biden and Trump are set to meet again for another debate on September 10, hosted by ABC News.