Thomson Reuters lists the 12 month forward p/e as 17.04. Per Ed Yardeni, there is only one time higher than this in the last 10 years and it appears to be in Q1 2015. If we make it to 18x per these numbers, then we'll see 2300.
WSJ is listing the 12 month forward p/e as 18.39. I am a bit suprised to see 18+ before the election, but it is what it is. 19x at 2247 and 20x at 2365.
Fundamentals are a bit more clear - the Citigroup Economic Surprise Index has turned sharply higher into positive territory after spending 18 months below the zero line. As longs as this is going up, dips will be bought.