Among them: Two incumbent Pennsylvania congressmen are on the defense amid questions about their ethics and personal relationships; and Maryland candidates for Senate are divided by race and gender.
Five delegate-rich states on the East Coast's "Acela corridor" vote Tuesday. Can front-runners Donald Trump and Hillary Clinton wrap up their respective nominations?
The campaigns of Republican presidential candidates Ted Cruz and John Kasich have coordinated their efforts in select upcoming primaries in a last-ditch effort to deny Donald Trump the GOP nomination.
Bernie Sanders campaigns in Connecticut ahead of the next set of primaries. Sanders is facing an uphill battle in Tuesday's contests. He needs to win at least 59 percent of pledged delegates if he hopes to overtake his rival Hillary Clinton and win the Democratic nomination. But Sanders and his supporters are vowing to fight on.
John Kasich and Ted Cruz will stay out of each other's way in three upcoming primary states. The nonaggression pact is an attempt to block Donald Trump from clinching the GOP nomination.
Donna Edwards is vying to be just the second black woman ever elected to the Senate. But not all of the state's black female leaders or African-American members of Congress are lining up behind her.
Five states in the Northeast go to the polls Tuesday. Bernie Sanders faces a tough challenge on the Democratic side, while Donald Trump leads GOP polls.