We've relaunched  "The Probability of 270" to the interactive electoral college map page. This feature works in tandem with your maps, as you create them, to tell you the probability that either candidate will reach 270 electoral votes based on the remaining states undecided on your map. The calculated probabilities for each state are derived primarily from current state by state polls, basically using the same methodology that underlies the 2012 election simulator  (which is also live for 2012). Therefore, it is subject to many of the same limitations as that tool, which you can read about on the simulator page.

You'll find The Probability of 270 underneath The Road to 270, both of which are below the interactive map. As a reminder, The Road to 270 calculates every critical path to 270 electoral votes remaining for each of the candidates. Both of these features will appear with 12 or fewer states remaining undecided on your map, where neither candidate has 270 and will dynamically update every time you change the status of one of the states in the map.