Sen. Ted Cruz (R-Texas) speaks to a crowd gathered at Liberty University in Lynchburg, Virginia, on March 23, 2015, to announce his presidential candidacy.

Please welcome the president of the future.

With Tuesday's addition of Mike Huckabee, the Republican presidential field for 2016 seems to be shaping up. But speculators have been busy for years trying to guess which candidates will be throwing their hats into the ring for 2020 and even into the 2030s.