Warren Laces Into Rivals as Iowa Campaign Grows Combative

DES MOINES — Displaying a new assertiveness toward her Democratic opponents, Elizabeth Warren laced into her chief political rivals, warning on Friday night that the country was in a “time of crisis” and arguing that Democrats would lose in 2020 if they nominated “anyone who comes on this stage and tells you they can make change without a fight.”

Speaking to thunderous applause during the party’s biggest Iowa political event of the year, Ms. Warren denounced candidates in the presidential race who opposed bold ideas in favor of more moderate...