Expect a contentious debate on Thursday when Hillary Clinton and Bernie Sanders go head-to-head in Brooklyn in the wake of what may be the most intense sparring of the Democratic primary to date.

The debate is an opportunity for the rivals to make an impression on voters before the Empire State picks a Democratic winner in its primary on April 19, a critical contest given the vast number of delegates at stake (247 for Democrats, to be precise). Clinton and Sanders both have a claim to the state, Clinton as a former New York state senator and Sanders as a Brooklyn native. As a result, the candidates will likely trot out their ties to the state in hopes of endearing themselves to voters. (The dynamic prompted Time to ask: “Who is More New York: Hillary Clinton or Bernie Sanders?”)

The debate—airing at 9 p.m. ET on CNN—could also get vicious. Tensions are running high between the two campaigns after a scuffle over who is more qualified to win the White House. It started when Sanders appeared to falter during an interview with the New York Daily News editorial board when pressed on policy specifics, including questions over how he would break up big banks. In the wake of that, Clinton was asked on MSNBC if Sanders is “qualified and ready to be president” to which she replied that the interview “raised a lot of really serious questions,” adding: “You can’t really help people if you don’t know how to do what you are campaigning on.” Sanders shot back in Philadelphia, saying: “I don’t believe that she is qualified.” As my colleague David Graham notes, Sanders’s critique was more semantic than substantive since it rested on criticism that Sanders has leveled at Clinton for a while. Still, the comments put a far sharper point on the case Sanders has been making against Clinton, and demonstrated his willingness to escalate the attack.