Iowa has been a fairly volatile state in the presidential primary campaigns -- for both parties. Hillary Clinton had the original lead there, then for a short time it looked liked Bernie Sanders was ahead there, and now Clinton has retaken a 7-point lead among Iowa Democrats.
It has been even more volatile for the Republicans. Scott Walker started off with a substantial lead in Iowa (which borders his own home state of Wisconsin). Bush, Paul, Fiorina, Christie, and Huckabee have also shown some strength there. Now they have all faded badly, and Walker has dropped out completely. Then it looked like Trump had achieved dominance among Iowa Republicans -- but now he has dropped back, and is second to Carson by 8 points. In the next three months, it wouldn't surprise me at all to have this pack of candidates shaken up more than once again.
The survey of Democrats was the Des Moines Register / Bloomberg News Poll -- done between October 16th and 19th of 402 likely Democratic caucus-goers, with a margin of error of 4.9 points.
The survey of Republicans was the Quinnipiac University Poll -- done between October 14th and 20th of 574 likely GOP caucus-goers, and has a margin of error of 4.1 points.
