When voters cast ballots in the presidential primaries, they are really voting for delegates.  Those delegates, in turn, are the actual people who will vote on the party’s nominee at the summer convention.  In a few states, candidates pick their delegates outright, but in most cases they have less control. Many delegates are elected by party members at local and state conventions. The candidates often conduct parallel campaigns to get their supporters named as delegates.  Here are examples of the variety of methods for selecting delegates used in different states. In fact, many states use two or more methods.  Wisconsin: Choose from approved list  Maryland: Delegates list candidate they support, only if candidate approves  Alabama: Delegates list candidate they support  Pennsylvania: Delegates do not list candidate they support  South Carolina: Through conventions, from prior delegates  Kentucky: Approve nominations made by committees  When they get to the convention, most delegates are “bound” to vote for the candidate voters have chosen in their state or district. But if no candidate gets the 1,237 delegates needed to win, subsequent votes will be held until someone does.  This is where the loyalty of each of the 2,472 delegates really matters. Most states “unbind” their delegates after the first or second vote. Then each delegate can vote for whomever they want. Some possibilities:  Delegates Selected By Candidates May Be Less Likely to Switch Sides  A Trump delegate from California ...  ... is hand-picked by Mr. Trump.  ... may continue voting for Mr. Trump, but could switch.  ... must vote for Trump on the first two ballots.  ... is hand-picked by Mr. Trump.  ... may continue voting for Mr. Trump, but could switch.  ... must vote for Trump on the first two ballots.  In a handful of states like California, which holds its primary on June 7, candidates handpick their delegates to the convention, making it more likely that they will stay true to the voters’ wishes even when they are unbound (for Californians, this occurs after the second ballot).  Delegates Chosen By Party Members Could Flip Their Support  A Trump delegate from Texas ...  ... is chosen by party members.  ... must vote for Trump on the first two ballots.  ... could switch votes on the third ballot.  ... is chosen by party members.  ... must vote for Trump on the first two ballots.  ... could switch votes on the third ballot.  In several states, including Texas, at least some delegates are elected through local caucuses and at the state convention. In Texas, the presidential candidates run what the state party’s assistant general counsel described as “36 separate mini-campaigns” in the state’s congressional districts to get their supporters elected.  Some Delegates Can Only Be Released by Winning Candidates  A Rubio delegate from Alabama ...  ... may change allegiance once released.  ... must vote for Mr. Rubio until he releases them.  ... must vote for Mr. Rubio until he releases them.  ... may change allegiance once released.  Some states do not unbind delegates after a certain number of ballots. In Alabama, delegates are elected on the primary ballot, listed next to the presidential candidate they support. They must continue to support that candidate at the convention until two-thirds of the delegation votes to change, or until the candidate releases them.Other states, like Alaska, unbind delegates if their candidate drops out of the race. Marco Rubio, who suspended his campaign in mid-March, sent a letter to the state party asking it not to release the five delegates he won there.  Some States Don’t Bind Their Delegates to Primary Results at All  A delegate in Pennsylvania ...  ... can switch at any point.  ... can vote for whoever they want.  ... can switch at any point.  ... can vote for whoever they want.  Roughly five percent of delegates will go into the convention free to vote as they please, including 54 from Pennsylvania.  Party Leaders Who Are Automatic Delegates Could Favor Anyone  National party delegates in states Trump won ...  … could eventually switch votes.  … must vote for Mr. Trump for at least one ballot.  … must vote for Mr. Trump for at least one ballot.  … could eventually switch votes.  Three party leaders from each state — the national committeeman, the national committeewoman and the state chairman — are automatically selected as delegates. States have different requirements for how long these delegates must remain bound to a candidate.  The potential for rule changes is another reason the nomination could come down to delegate loyalty. A rules committee, made up of representatives from each state, can propose pretty much any change to the rules before the convention begins, and it takes just a majority of convention delegates to approve them.  Ron Paul delegates from Maine protested at the 2012 Republican National Convention in Tampa. Damon Winter/The New York Times  In 2012, supporters of Representative Ron Paul, the last remaining Republican challenger to Mitt Romney, fought to secure delegates at local and state conventions, particularly in states where those delegates were not tied to election results.  The Iowa delegation, for example, was made up primarily of Mr. Paul’s supporters, even though Mr. Romney and Rick Santorum essentially tied for first in the state’s caucuses.  These tactics did not go over smoothly at the convention. Half of Mr. Paul’s delegates from Maine were unseated, and his supporters erupted with anger after Mr. Romney’s allies passed new rules to prevent Mr. Paul from qualifying for the first nomination vote on the floor.
The rules for how Republican delegates are selected could end up turning votes for one candidate into delegates who will support another candidate at the convention.