However, upon further inspection the American Research Group (ARG) polls shows little movement, if any, among the major contenders from December (before any of the major announcements) to January(post-annoucements):
In December, the numbers looked as follows:
The margin of error in the latest poll is +/-4%.
The biggest 'mover' in the poll, on a percentage basis, was "Undecided", which jumped from 8% to 13% (an increase of 63%). Perhaps "likely Iowan caucus goers" realize that there's still a year to go before caucusing commences.