In nearly every presidential primary, a few candidates attract a lot of news media attention even though they have almost no chance to win the nomination. Sometimes they even lead national polls or win states, but invariably their appeal is too narrow to allow them to build the broad coalition necessary to unite a diverse party.

Ted Cruz, the Texas senator and Tea Party favorite, who on Monday became the first candidate to formally enter the race, has seemingly been on track for this role since he first ran for the Senate in 2012. He is the darling of conservatives in a conservative party. But he remains a long shot, at best.

The most interesting question about Mr. Cruz’s candidacy is whether he has a very small chance to win or no chance at all.

Political scientists argue that the single most important determinant of the outcome of the nomination is support from party elites: those operatives who can staff a winning campaign; the donors who fund it; the elected officials and interest group leaders who bestow the credibility necessary to persuade voters and affect media coverage.