Silver's prediction is based on a wide array of polling, none of which is his. He's a math guy, not a pollster. Any personal or subjective thoughts he may have is not factored in, obviously. And after getting 99 out of 100 states correctly in the last 2 elections, I would say is better than most, if not all who do his type of work.
UTfanatic that moment when aggy's title hopes are down the crapper just like every other year of their lives (my apologies if there are any 77+ year old posters on this board):
But more importantly, Nate Silver (who is the best in the biz, period) has him up to a 35% chance of winning the election. He was at like 15% a few weeks ago. Quite a surge.
If I recall correctly (and I assuredly do), I predicted 3 or less district losses in 5 years. And that both McCain and Adams would be studs as freshmen. Silly me!