Tonight is a primary night with elections in Kentucky, Pennsylvania, Arkansas and Oregon. Polls close at (all eastern times)

Kentucky: 6 pm
Pennsylvania: 8 pm
Arkansas: 8:30 pm
Oregon: 11 pm

Election results for Kentucky can be found at AP or Politico.

The big races are the contested Senate primaries in KY, PA and AR, and the special election in PA-12 Congressional district to replace Democrat John Murtha. David Dayen has a primer on the races to watch this evening and so does Swing State Project. Ben Tribbett examines what you should be watching for in the Arkansas primary.

Results should start coming in from Kentucky very shortly. (Feel free to post your prediction for the results this evening in the comment sections.)

6:03 – Greg Sargent is reporting that turnout has been very light in Pennsylvania, which should favor Joe Sestak over Arlen Specter.

6:24 – The very first results are just starting to come in from the eastern part of Kentucky. With less than 1 percent of precincts reporting in the Senate, it is Democrats Dan Mongiardo 50.5 – Jack Conway 37.7, and Republicans Rand Paul 49.9 – Trey Grayson 43.3.

6:48 – With just over 1% it is Mongiardo 48 – Conway 39 and Paul 51 – Grayson 42. The results are coming from what should be a more Grayson heavy part of the state. I would not be surprised if the Republican Senate primary is called very early this evening.

7:00 – All polls are now closed across Kentucky. The state has parts in both the eastern and central time zones.

7:10 – About 6% reporting Mongiardo 45- Conway 42 and Paul 55 – Grayson 39. Things are looking very good for Paul.

7:20 – 13% reporting Mongiardo 40 – Conway 47 and Paul 51 – Grayson 34. I agree with Nate Silver you can basically call this election for Rand Paul at this point.

7:40 – It looks like Republican Andy Barr will easily win the right to take on incumbent Ben Chandler in KY-6. With 30% reporting he has 67% with all other candidates in the single digits.

7:48 – The AP finally called it for Rand Paul. 32% reporting Paul 59 – Grayson 37. Paul might actually out perform polling. This is not a good day for Mitch McConnell. He might be the most powerful Republican in Washington right now but his endorsement of Grayson basically meant nothing.

Ron Paul helped get a form of audit the fed passed, won several Republican 2012 straw polls, and just had his son dominate in an important Senate primary. Things are going pretty will for Ron Paul right now.

8:00 – I have started part 2 of my coverage here