Bush Cuts Costs, Carson Eclipses Trump in Iowa and G.O.P. Frets

A beleaguered Jeb Bush slashed his campaign spending. Donald J. Trump lost his lead in Iowa. And a surging Ben Carson galvanized his support among social conservatives.

With Hillary Rodham Clinton emerging as the unrivaled leader in the Democratic contest, the unruly Republican presidential field suddenly seemed to lack a center of political gravity on Friday, leaving party strategists and voters to fear a long nomination fight that could end with a damaged standard-bearer facing a more unified left.