Bruce Barry on Nate Silver's latest analysis:

In 10 of 18 states the red grows redder — a polling lead for Mitt Romney that exceeds John McCain's 2008 margin of victory. In the other seven, all still with Romney ahead, the redness has paled — a smaller Romney edge in polling now compared with McCain's margin four years ago. The two states with the biggest movement from red to blue (some may prefer "from red to pink") are South Carolina followed by, yes, Tennessee! — the latter showing the red margin of advantage cut in half.

If you're wondering about the extent and quality of polling to this point in Tennessee, the answers are sufficient and quite good. Silver's weighted number for Tennessee relies mainly on two surveys: a YouGov poll earlier this month (finding Romney +8 among registered voters) and a Vanderbilt poll in May (Romney +7 among registered voters).