Michele Bachmann's Iowa-centric strategy for keeping her White House bid alive took a big hit Tuesday in a pair of new polls showing her support shrinking among probable Iowa caucus goers. A Public Policy Polling survey had her tied for fifth with only 8 percent suppport. That's a 10-point crash from her GOP straw poll win in August, when the same poll had her in third place with 18 percent support. A separate NBC/Marist poll on Tuesday had Bachmann at 10 percent, good enough to tie for fourth with Rick Perry. The Marist poll keeps Mitt Romney in the lead at 23 percent, followed by Herman Cain at 20 percent. Public Policy Polling's new frontrunner in the Hawkeye State? Cain, now the first choice of 30 percent of Republican voters in Iowa. Romney, at 22 percent (and up three points from August) is holding on to second place. Following behind are Ron Paul, at 10 percent, Perry, 9 percent, and Bachmann at 8 percent, tied with Newt Gingrich. This is not great news for Perry, who led with 22 percent in in the Public Policy poll soon after he entered the race in August. It's amazing news for Cain, who has gained 23 points since August, much of that apparently at the expense of Bachmann and Perry. One caveat for Cain: As Bachmann can attest, Republican voters seem to be swinging all over the place as they search for a 2012 standard bearer. This from the Public Policy poll's authors: "Over the course of our last four polls in the state we've found four different leaders: Mike Huckabee, then Romney, then Perry, and now Cain. And if we'd done a poll any time in July or early August we probably would have found Bachmann in the lead to make it five leaders in five polls."