A chance at puttin Cruz into office.
Perhaps they think the 15% is the only group that really counts, but I suspect not. I suspect it's simply a "religious" thought process brought into the messy world of politics (not in the sense of any particular religion or belief system, but in the sense that they approach political matters with the same thought process they approach religious matters with). In a religious thought process, there is great glory and even greater victory (in a different realm) from going down to defeat, even unto death, with your "principles" 100% intact -- with absolutely no compromise whatsoever. Taking religious thought processes into politics means that you do not compromise one iota and if it so happens you go down in total flames, hopefully you can take everything down with you like Samson or like the Christians martyred in the Coliseum. Using that sort of thinking, there is virtue in the glorious defeat.
I think that is what we are seeing here, and it is pretty common the further out on the political bell curve you travel (Camejo and his supporters are no less "religious" in their thinking). The bible, for just one example, is chock full of encouragements for forgo compromise -- "if you are lukewarm, I will spit you out".
For me, I don't believe "religious thinking" works well in modern democratic politics, where security, caution and the middle road dominate the selection of governmental leaders. The one who seems most secure, the one who will not change things too drastically, will most often be the one selected by the mass of voters. There is security in sameness, so if you are running "to change" things, to get the votes you need you will need to convince people that yes, you will change this or that, but you won't change everything, you won't be drastic in your prescriptions for change. People don't like to have to deal with new realities, they are comfortable operating in the familiar.
And anyway, most of the McClintock voters who will change will do so without any proding from McClintock himself. Those that are in tune to the election and who think more politically than religiously will move over on their own. As for those who think more religiously, there is nothing in heaven or hell that would make them change anyway.
They have chance to feel good, really good, about themselves. There are standing up for their "principles." It used to be that ultra conservatives were for "doing good." The modern, New Age, Ultra Conservatives are all about "feeling good." They are the 21st century Hippies.