Any general election poll in Pennsylvania, Arkansas, or Kentucky taken over the next two weeks. The positive press that comes with winning elections distorts everyone's polling responses, so the polls will be very volatile over the next few weeks. Wait until June and see what they say then.
Update: and yes, if you insta-poll the Blumenthal race you'll end up seeing him tank. When combined with Rasmussen's clear GOP lean, he's probably looking at an 8 to 10 point lead in the immediate wake of the crisis. Things could go up or down from here, but he's certainly not dead in the water.