URBANDALE, Iowa — From D.C. to Des Moines, Marco Rubio supporters believe he is the least like Donald Trump of all the top-tier Republican presidential candidates.

They see him as optimistic rather than voicing gloom and doom, cheerful and positive rather than dark and negative, welcoming rather than fearful and capable of expanding conservatism’s appeal beyond angry white men. Those are some of the things the 1,000 or so people who turned out to see Rubio at the Ramada Tropics Resort and Conference Center on Saturday night like him about him.