The polls are produced to create news. None of these polls are "likely voters". However, the recent Gallup Poll has Romney up by 2%.
The undecided break for the challenger in almost every presidential election, according to Dick Morris. According to the Gallup poll, thats amounts to 18% or less. Interesting comments about the polling too.
The right track-wrong track percentage is a important indicator on which way the public is going to vote, like in 2010.

http://www.gallup.com/poll/153902/Romney-Obama-Tight-Race-Gallup-Daily-Tracking-Begins.aspx

Daily Kos ordered a poll on the Scott Walker and when he jumped ahead, they apparently found out the pollster recorded "likely voters" Usually those polls come out a few weeks before the election.