Thirty-four Senate seats, all 435 House of Representatives seats and 36 governorships are at stake. There are also a number of referendums on a wide range of local issues. Polls predict modest gains for Republicans, in line with the precedent that the party in the White House almost always loses when the presidency is not at stake.
The election will be viewed as a barometer of how Americans view the White House sex scandal. A big win for Republicans could rekindle their enthusiasm for the impeachment of President Clinton, for which 67 Senate votes are needed.
If Democrats hold their own it could slow the momentum of the impeachment effort. Republicans currently control the Senate 55-45, and the House 228-206 with one independent. First polling stations open today at 6 a.m. (local time). Exit polls around midnight (Irish time).