Take Arizona, where Trump won all 58 of the state’s delegates on Tuesday. Three of the delegates are reserved for current party leaders. The other 55 are chosen through a tiered system in which previously elected precinct committee members hold local conventions on different dates to choose state delegates, who then attend a state convention on April 30, where they choose the national delegates who will actually vote for the Republican nominee.

Got it? Now, multiply that across dozens of states, districts and counties, and you get an idea of the scale of the challenge.

Trump, Cruz and Kasich are all already working to win over delegates and direct the process in states where they’ve yet to be chosen. But experts give Cruz an early edge, thanks to his extensive grassroots network and (in comparison to Trump) closer ties with party leaders, who often have an outsized role in the selection process.

“That’s where Cruz has the advantage,” Josh Putnam, a political scientist at the University of Georgia who researches delegate rules, told MSNBC. “He seems better positioned, at least at this point, to identify folks sympathetic to him and then get them elected to those delegate spots.”

Unlike the state primaries and caucuses, we may not know who is winning the delegate race for months. While campaigns will try to put up their own loyalists, parties frequently choose slates of established officials and donors without regard for whom they might support at the convention itself.