Assuming no Trump run:
Josh Hawley ✓
Nikki HaleyRick ScottTom CottonMike Pompeo
Ted CruzHawley pretty quickly beats out other populist claimants who drop out after Iowa, becoming the Obama-Trump voter candidate with sizable evangelical and some moderate support. Haley and Scott (who functions as a more serious Bloomberg) split the bulk of the moderates, Cotton's base is unstable á la Elizabeth Warren, Pompeo is an even weaker version of Cotton, Cruz's base shrinks to Mormons disaffected by Trump's eventual backing of Hawley.
By the end, everyone consolidates behind Hawley, who promises cabinet positions to most of his opponents.