WASHINGTON — Veteran Indiana Sen. Richard Lugar lost a bitter challenge from the right flank of his own Republican Party in primary voting Tuesday, ending his nearly four-decade career in the Senate.

Also Tuesday, North Carolina voters weighed a gay-marriage ban and Democrats were picking a nominee to challenge Republican Wisconsin Gov. Scott Walker in a June recall election, contests that overshadowed Mitt Romney's unstoppable progress toward the GOP presidential nomination.

Romney won the Indiana GOP presidential primary and was all but certain of victory in two other states, drawing close to the 1,144 delegates he needs to clinch the nomination.

Even Romney, the former Massachusetts governor, was essentially ignoring primaries that were likely to hand him 100 or so delegates of the 288 he still needed heading into Tuesday's contests. He spent the day campaigning in Michigan, where he castigated President Barack Obama as an "old-school liberal" whose policies would take the country backward.