What is a brokered convention?
A contested convention run by party elites could sink Trump’s chances at the nomination, and many establishment Republicans loathe Cruz as much or more than Trump, meaning they’d likely look for any other option.
That’s why both Marco Rubio and John Kasich have been openly talking up the possibility of a contested contention — and why Trump and Cruz have been critical of it. It’s likely the only way Rubio or Kasich (or someone else palatable to moderates and the establishment) might wind up as the nominee.
Also from Mashable: Brokered convention explained
Reality check: If Trump emerges as the clear favourite, a brokered convention would just mean that the party does not want as its nominee the candidate with the most support. One thing that outcome would make clear is that the rank and file do not count for nearly as much in the party as the donorcrats. What then happens to door-to-door campaigning?
But then maybe door-to-door doesn’t matter so much anymore. We shall see.
See also: High tech unites with donorcrats against Trump. In other news, snow melts in spring.