Third-party Libertarian candidates threaten to siphon votes from Republicans in competitive states and could imperil the party's chances of holding its narrow majority over Democrats.

When Americans cast their ballots in this year's midterm elections, they'll not only be picking who represents them in Congress, but also weighing in on a range of topics that could change their state laws and constitutions.

The Supreme Court cleared the way Thursday for New Hampshire to fully ban the use of student IDs for voting during the midterm elections.