Not all delegates who have been selected to represent Mr. Trump are fans of his.

The majority of delegates are being selected through a series of elections at local and state conventions. In some states, some of Ted Cruz’s supporters have been selected to represent Mr. Trump at the convention. Mr. Trump has called them “double agents.”

This may not matter at first because they will be bound to Mr. Trump during the first nominating ballot. But if no candidate reaches 1,237 delegates and there is a second ballot, these delegates will be free to vote as they please.

Georgia At least 11 of the delegates who will be bound to Mr. Trump at the convention favor another candidate. South Carolina Mr. Trump won all 50 of the state’s delegates during the primary vote, but of the delegates selected so far, just one has expressed support for him, according to local news reports.

And it looks like the same thing might happen in other states.

Less than half of North Carolina and Iowa’s delegates have been selected at district conventions so far, but most of the ones who have been selected support Mr. Cruz, even though he won only about a third of delegates in those states.

Again, these delegates must vote for Mr. Trump on the first ballot, but they will be free after that.

North Carolina Mr. Cruz won just 27 out of 72 delegates in the state’s primary. But of the delegates selected so far, the majority are reported to favor Mr. Cruz. Iowa Mr. Cruz won just 8 out of 30 delegates in the state’s caucuses. But of the delegates selected, nearly all of them are reported to favor Mr. Cruz.

Trump was out-organized in states that did not have a primary vote.

Three states are not holding a primary election or a caucus for voters to weigh in on a nominee. Instead, party members at conventions directly select delegates, some of whom will be bound, or required, to vote for a candidate at the nominating convention.

So far, Mr. Cruz’s campaign has proved much better at courting these delegates and has almost completely shut out Mr. Trump in these states.

Colorado Wyoming North Dakota

Trump won the Louisiana primary but may end up with fewer delegates.

Mr. Trump has threatened to sue over the delegate selection in Louisiana, where 10 delegates are not currently bound to any candidate at the convention. All 10 of the people selected for those slots reportedly favor Mr. Cruz — another indication that the Cruz campaign has been much better at working within the party’s complex system of rules than Mr. Trump’s.

Tennessee chose two delegates who have criticized Trump in the past.

In Tennessee, most delegates were chosen on the primary ballot (with their candidate of choice listed), but about a quarter of them were appointed by a party committee.

The committee selected six delegates to represent Mr. Trump for at least the first two ballots at the convention, and while they followed some of his campaign’s suggestions, two of the delegates are people who have criticized him in the past.

Indiana hasn’t voted yet, but Trump supporters may be shut out of the delegate selection.

Indiana’s delegates were appointed by party leaders earlier this month, even though the state’s primary election isn’t until May 3. The selection process in Indiana tends to reward longtime party activists, and there is evidence that very few of those chosen favor Mr. Trump, and that many are supporters of Gov. John Kasich of Ohio.