The viewers have spoken: Ready or not, the next presidential campaign is here.

NBC’s presidential debate in Miami on Thursday — seven months before the Iowa caucuses — broke the record for the biggest television audience for a Democratic primary matchup, a sign of widespread early engagement with the 2020 race.

Nearly 18.1 million Americans watched live on NBC, MSNBC, and Telemundo as 10 candidates clashed. The broadcast included a riveting exchange between Senator Kamala Harris of California and former Vice President Joseph R. Biden Jr.

The ratings, released by Nielsen on Friday, beat the 15.5 million viewers who watched the previous record-holder for a Democratic debate, a meeting of five candidates on CNN in October 2015. The audience was also greater than the one for Wednesday’s round of the Miami debate, which featured fewer star politicians and was seen by roughly 15.3 million viewers.

The numbers are a reminder of the power that prime-time television still holds to gather a national audience, even in an age of fractured and niche media platforms. And for Americans barely two and a half years removed from the ubiquity of the 2016 campaign, the ratings may provide the bracing realization that the next contest is already well underway.