Vox Populi Iowa caucus poll:
http://www.usnews.com/news/blogs/run-2016/2014/06/10/iowa-remains-in-flux-for-republicansDems
Hillary Clinton 65%
Joe Biden 18%
Elizabeth Warren 12%
Andrew Cuomo 3%
Martin O'Malley 2%
GOP
Jeb Bush 18%
Mike Huckabee 15%
Paul Ryan 13%
Rand Paul 12%
Marco Rubio 11%
Rick Santorum 10%
Ted Cruz 9%
Chris Christie 6%
Scott Walker 6%
Those are from the separate Dem. and GOP subsamples. But they also polled a few questions for the general Iowa electorate, including on Bergdahl:
http://www.poppolling.com/index.php?polls-news&a=view&article_id=13#.U5ewA8alD4Y"49% of Iowans oppose the Obama Administration’s decision to exchange five high-level Taliban terrorists for American Prisoner of War Sgt. Bowe Bergdahl, with 26% supporting."