CLEVELAND, OH – AUGUST 06: Republican presidential candidates (L-R) Sen. Marco Rubio (R-FL), Ben Carson, Wisconsin Gov. Scott Walker, Donald Trump, Jeb Bush, Mike Huckabee and Sen. Ted Cruz (R-TX) take the stage for the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Scott Olson/Getty Images)

Trump may win most primaries and may have the most delegates, but, if he does not end up with a majority of delegates, then he is likely to loose in the final analysis.

In United States politics, a brokered convention is a situation in which no single candidate has secured a majority of delegates (whether those selected by primary elections and caucuses, or superdelegates) prior to the first vote for a political party’s presidential candidate at its nominating convention.

Once the first ballot, or vote, has occurred, and no candidate has a majority of the delegates’ votes, the convention is then considered brokered; thereafter, the nomination is decided through a process of alternating political horse-trading, and additional re-votes.[1][2][3][4] In this circumstance, all regular delegates (who may have been pledged to a particular candidate according to rules which vary from state to state) are “released” and are able to switch their allegiance to a different candidate before the next round of balloting. It is hoped that this extra privilege extended to the delegates will result in a re-vote yielding a clear majority of delegates for one candidate.

Superdelegate votes are counted on the first ballot. Although the term “brokered convention” is sometimes used to refer to a convention where the outcome is decided by superdelegate votes rather than pledged delegates alone, this is not the original sense of the term. Like a brokered convention, the potentially decisive role played by superdelegates can often go against the popular vote from the primaries and caucuses.

Brokered conventions in history

Before the era of presidential primary elections, political party conventions were routinely brokered. The Democratic Party required two-thirds of delegates to choose a candidate, starting with the first Democratic National Convention in 1832, and then at every convention from 1844 until 1936. This made it far more likely to have a brokered convention, particularly when two strong factions existed. The most infamous example was at the 1924 Democratic National Convention (the “Klanbake”), where the divisions between Wets and Drys on Prohibition (and other issues) led to 102 ballots of deadlock between frontrunners Alfred E. Smith and William G. McAdoo before dark horse John W. Davis was chosen as a compromise candidate on the 103rd ballot. Adlai Stevenson (of the 1952 Democratic Party) and Thomas E. Dewey (of the 1948 Republican Party) were the most recent “brokered convention” presidential nominees, of their respective parties. The last winning U.S. presidential nominee produced by a brokered convention was Franklin D. Roosevelt, in 1932.

Read further in Wikipedia about Brokered Conventions