These charts come from a new Economist / YouGov Poll done between January 10th and 12th with a random national sample of 1,000 adults. The poll had a margin of error of 4 points (and would be a little higher when only Republicans or Democrats are considered).
Mitt Romney has certainly looked like he will toss his name into the ring for a third time, and it looks like he has an early lead of 16 points over Bush, who finished in second place -- if 28% can be considered a real lead. That means 72% of Republican voters are not yet ready to crown him again. Personally, I think the sting of their second loss to President Obama is still too fresh in their memories, and I doubt they'll give Romney another chance -- at least not in 2016. It's anybody's guess though as to who the nominee will be.
There's still no doubt on the Democratic side though. Although Move On and Democracy for America have been trying to drum up support for Elizabeth Warren (in spite of the fact that she says she will not run), she only gets 17% of the vote (44 points less than Hillary Clinton). It still looks like all Hillary has to do to get the nomination is to ask for it.