In one of the bigger primary days of the year, eight states hold primaries today. Arizona, Minnesota, New York, Rhode Island, Delaware, Maryland, New Hampshire, Vermont, and Wisconsin vote today. [CORRECTION: as reader "fatman" points out in the comments, there are actually NINE in that list]

There will also be special elections Thursday and Friday to fill spots on two Ohio district ballots, and Washington state and Massachusetts finish off the primary season next Tuesday. Hawaii does hold the absolute "final" primary on September 23rd.

The nationally most-important races we will be watching tonight include the Rhode Island GOP Senate contest between incumbent Sen. Lincoln Chaffee and challenger Cranston Mayor Steve Laffey. Laffey has the conservative credentials, but the GOP establishment is backing Chaffee as the only chance to hold the seat in "dark blue" RI. Late polls have this one too close to call.

In Maryland, the Democratic Senate nomination for the seat vacated by retiring Democratic Senator Paul Sarbanes (whose magnum opus, the Sarbanes-Oxley law, is the classic example of why all legislation should be periodically subjected to cost-benefit analysis) is up for grabs. Long-time congressman Rep. Ben Cardin faces Kweisi Mfume, former congressman and recently President of the NAACP. The polls have been all over the place on this one, so we'll just have to see the "only poll that counts" tonight. The winner will face off against presumptive GOP nominee Lt. Gov. Michael Steele.

Arizona hosts one of the key House primaries in its 8th district, as 11-term incumbent Rep. Jim Kolbe is stepping down to run for Governor [CORRECTION: as reader "doug" points out in comments, Kolbe isn't seeking higher office]. State Sen. Gabby Giffords is heavily favored to win the Democratic nomination, but the Republican side is very interesting. Outside money has been coming it to help both former state Rep. Randy Graf and state Rep. Steve Huffman. Graf is being backed by Rep. Tom Tancredo and Bay Buchanan for his tough anti-immigration stance, while national and state Republican parties are supporting the more moderate Huffman, a former aide to Kolbe, who is thought to have a better chance of holding the seat in the general election. Polls had Graf in the lead, but short of a majority, so the race may depend on the supporters for the other "also-ran" candidates.

Be sure and check here often tonight for the latest updates.