Bitter foreign policy debates over Israel and Iran are fracturing the Democratic and Republican parties, creating powerful wedge issues that are reshaping the battle for control of Congress this year and could affect the 2028 presidential election.The dispute among Democrats, in particular, has already left a lasting mark on the midterms. Israel’s growing unpopularity since the war in the Gaza Strip began nearly three years ago emerged as a dominant force last week, when two incumbent House Democrats in New York lost to primary challengers who had cast them as insufficiently critical of the U.S. ally.And both U.S. support of...