A reader writes:
You seem to be using the phrase "brokered convention" to describe a convention with no de facto nominee. "Open convention" would be more accurate.
A brokered convention is a subset of open conventions – that is, one whose nominee is determined by brokerage among a small group of leaders. That is, a brokered convention has brokers. In an open convention in the modern era, who would the brokers be? The candidates themselves, or their campaigns? Doubtful – if they couldn't win a delegate majority at the polls, they're unlikely to be able to do so in the metaphorical smoke-filled rooms of the convention. The party's Washington establishment? Them and what army? That is, how many delegates does anyone who might pass as a party leader control? The answer is a little over 100.
There is no precedent for an open convention in the modern primary era, so we simply don't know whether such a convention could be brokered – or even if it could be, whether it would be. Given how delegates are selected, and the lesser institutional loyalty they tend to have to any figure or machine within their party than in the pre-primary era, it seems most likely that any deal-making would be done by and among state delegations and cross-state informal coalitions (Texans and Californians trying to stick together, say, or a Tea Party caucus arising). That is to say, it would be the delegates themselves, and if so, then there would by definition be no broker.
Will Tampa be an open convention? Quite possibly. Will it be a brokered convention? We don't know; it could be an open convention that selects a nominee without brokering.