Uses the Wikipedia definition of presumptive nominee:

In United States presidential elections, the presumptive nominee is a presidential candidate who is assumed to be their party's nominee, but has not yet been formally nominated or elected by their political party at the party's nominating convention.[3][4] Ordinarily, a candidate becomes the presumptive nominee of their party when their "last serious challenger drops out"[5] or when the candidate "mathematically clinches—whichever comes first. But there is still room for interpretation."[6] A candidate mathematically clinches a nomination by securing a simple majority (i.e., more than 50 percent) of delegates through the primaries and caucuses prior to the convention.[3][4] The time at which news organizations begin to refer to a candidate as the "presumptive nominee" varies from election to election.[6] The shift in media usage from "front-runner" to "presumptive nominee" is considered a significant change for a campaign.[6]