First up is Texas. To be on the ballot as an independent, Mr. Trump must file, by May 9, a declaration of candidacy, slate of electors and signatures from roughly 80,000 registered voters—1% of state turnout during the 2012 presidential contest.

A flurry of deadlines follows in June: Colorado on the 6th, Vermont the 16th, North Carolina the 24th, Illinois the 27th, Rhode Island the 29th and New Mexico the 30th. Five more states close before the convention is gaveled to order: Georgia on July 12 and Florida, Indiana, Oklahoma and South Carolina on July 15.

Rhode Island and Vermont merely require a declaration of candidacy and a thousand signatures, but the others demand more—from 5,000 signatures in Colorado to nearly 90,000 in North Carolina.

One additional state’s deadline comes during the GOP national convention. By Thursday, July 21, the day currently planned for the nominee’s acceptance speech, an independent candidate would have to submit roughly 30,000 signatures in Michigan, which has 16 electoral votes.