[CA Conservative]

Actually, according to the way Rule 40b is written, it would be possible (not likely, but possible as the rule is written) that Trump could fail to have his name placed in nomination. The rule is not that you have to win a majority of bound delegates in 8 states. The rule is that you have to get a majority of the delegates in 8 states to sign a statement of support for you before each ballot. And just because a delegate is bound to a particular candidate for the ballot doesn't mean they are obliged to sign the statement of support for that candidate.

So it would be possible, if Cruz or Kasich were to get a majority or even a plurality of the delegate spots filled with their supporters in the states where Trump has a majority of bound delegates, that Trump might not be able to get majority support from 8 states to get his name placed in nomination... as I said, I don't think it likely, but the rules would allow it.

[Sacajaweau]

The bound delegates and their statement are not separate. The statement is the acknowledgement in writing.

[5th MEB]

Sounds like a pretty stupid rule to me.
“You won my state, but now you gotta get me to sign a statement of support, watta ya gonna do if I don’t”.

[Lurkinanloomin]

If they try that kind of chicanery they will be finding out if you can have a political party without voters.

[TomGuy]

from: RNC Convention ‘Rule 40’ May Have Unexpected, Shocking Result

So according to the rules, Trump is the only candidate—at this time—who qualifies to be nominated.

A similar claim that Trump has reached the magic 8 number is in this WSJ article:

40 Is the New 1,237

It seems that Trump has met the Rule 40 requirement, as of April 1. Cruz had not. Kasich would have to win all of the delegate in seven of the remaining states.