Below is a chart showing the 2016 Republican presidential primary dates by state, along with the voting rules for each state.  Generally, states have a winner take all system, where the candidate with the greatest plurality gets all the delegates, or they have a combination of statewide winner take all with winner take all by congressional district, or they have proportional voting rules.

A few states like Wyoming, Pennsylvania, and South Dakota choose unbound delegates, who are not obligated to support a particular candidate, so anything can happen there.

There are a total of 2,470 delegates to the convention, and 1,236 are needed to win.

I have simplified a few things in the chart below.  In each state, anywhere from zero to three of the total delegates are chosen but not bound to their candidate, but for simplicity's sake, I included them all in the state totals.  Different states have different thresholds for winning any delegates proportionally, usually 15% or 20%, and some states elect delegates who then declare for candidates.  I treat that last group as "proportional" for categorization purposes rather than "winner take all."

I also feel that states that decide candidates by "winner take all/congressional district" are more likely to be like "winner take all" states then they are to be similar to proportional voting states, since a candidate's supporters are less likely to be mostly aggregated in individual congressional districts of a state (though in some cases it will happen).

Looking at the chart, we can see that there are 1,427 delegates decided proportionally, 438 by winner take all, and 470 by state winner take all combined with congressional district winner take all, as well as 128 unbound delegates from Pennsylvania, Wyoming, and South Dakota.  (But remember that as part of the numbers above, many of the other states also have 0-3 unbound delegates.)

So where does that leave Donald Trump?  If the primaries were held today, and he got 25% of the vote, he'd take 356 of the 1,427 proportionally decided delegates.  With that 25%, which would be the largest plurality of any candidate, he'd take all 438 winner -take-all delegates (including all of Florida's, heh heh).  And he'd probably take most of the 470 "winner take all by CD" states – say, 400 of those.  That's a total of 356 + 438 + 400, which equals 1,194 delegates.  Figure he gets another 36 from the 128 delegates of the three uncommitted states.  That brings him up to about 1,230.

Twelve hundred thirty-six are needed to be nominated.  That means that by this very, very rough estimate, if the polls don't change, Donald Trump is just on the edge of getting what he needs to avoid a brokered convention and to be nominated.  He also needs to win a plurality in every state, even in some Southern states, where polls have shown Ben Carson ahead.

What conclusion can you draw from any of this?  If Trump goes up or down even 3% or 4% in national polling, that will pretty much decide whether there will be a brokered convention or not.

This article was written by Ed Straker, senior writer of NewsMachete.com, the conservative news site.