AHC & WI: independent Deseret in a Trent War TL

I'd like to be clear from the outset: no war between the Union and Deseret prior to the ACW (at least nothing more than OTL Utah War). If anything, Deseret should be a Union ally/puppet/satellite state.

This is a two-parter:

The challenge is for Deseret not to join the Union prior to the ACW. Tell me how and why it continues not to join.

Then tell me how Deseret might behave during and after a Trent War in Union victory, defeat, and draw scenarios. Accounting for how the Trent War happens is not part of the challenge (it's been discussed enough in other threads). How will the various powers involved treat Deseret during and after the war? What do you think would be the ultimate fate of the country?

The first question in my mind would be to ask which US President (either as an 1848 candidate or as Taylor's VP when he dies) would be the best for the challenge and how an 1850-ish compromise would impact the Mormons' chances of admission to the Union.

No thoughts? Who's the most anti-Mormon politician who would never want to see them in the Union who could become POTUS?