I’m not sure what you mean about the deadline. Cruz is on the ballot or whatever they call it.
The sodden bent of this thread was that somehow all these hidden evangelicals will help Cruz pull a convention rabbit out of his ass, and that somehow Kentucky factored yugely into this preposterous hypothesis; but witness that Kentucky switching to a caucus system does not help Cruz in the slightest, ironically because Rand saw fit to create a Dec. 31, 2015 deadline for signing up!
Now, 41 days into 2016, and with Rand out, no candidate can 'load up' the caucus with last-minute supporters. Therefore, that 2015 sign-up deadline only aids retail politics - as it has been proven in Iowa must be done in caucus states - and yet not one single candidate has campaigned in the Bluegrass.