For Charlie Gruschow, chairman of Tea Party of America and a longtime Herman Cain supporter in Iowa, the latest allegation may be the last straw.

“I’m not sure,” he said earlier this week when asked if he remains a Cain backer. “I don’t know. I’ve had three or four days to process some of this information, and . . . I’ve been a Herman supporter for well over a year now, so I’m hoping that — I just don’t know what to make of these most recent allegations.”

Gruschcow believes that the allegations are not “credible” and that Cain is innocent. Considering the overall situation in Iowa, he says that Cain supporters are “pretty strong” but concedes Ginger White’s allegation has caused “some discouragement.”

Yesterday, according to the Associated Press, Gruschow had switched to being a Newt Gingrich supporter. And after a disastrous month that combined the sexual allegations with policy blunders, it’s easy to believe that Gruschow will be followed by other Iowa Cain supporters, assuming Cain stays in the race. Tim Albrecht, communications director for Iowa Republican governor Terry Branstad and Romney’s Iowa communications director last cycle, is confident Cain’s Iowa moment is over — and partially blames Cain’s lack of retail politics in Iowa.

“The people who stood by him thus far, this latest allegation likely won’t budge them, but they’re few in number,” Albrecht says. “He never visited here enough to build the organization he needed to organize in the state’s 1,784 precincts. And now, with all the allegations, Iowans only looked through the filter of the media. So even when it first started out and he had some defenders, a lot of Iowans were inclined to just believe what they saw in the media because they weren’t seeing him in Iowa.”

Pair the allegations with Cain’s other stumbles, such as his faltering answer on Libya in an editorial-board meeting with the Milwaukee Journal-Sentinel, and it’s becoming too much for even his ardent Iowa supporters, observes Craig Robinson.

“His supporters were very passionate,” says Robinson, editor of TheIowaRepublican.com and a former Iowa GOP political director. “But I think that he is giving them plenty of examples of where he is not a serious candidate, and I think a lot of them have started to look elsewhere.”

Jeff Jorgensen, Pottawattamie-county GOP chair, is among those undeterred. “I’m totally backing Mr. Cain,” he says, adding later that “we’re not going to let the media determine our nominee.”

Calling Cain an “inspiring candidate,” Jorgensen continues, “If he chooses to stay in the race, I’m going to be working hard to see that he overcomes these obstacles.” Like Gruschow, he doubts the credibility of the accusations, commenting that all the women who have come forward have “questionable backgrounds.”

In Iowa, the campaign has “lost a few supporters,” concedes Steve Grubbs, Cain’s Iowa chairman. “It’s slowed down our momentum,” he says of the charges, but notes that “at the end of the week, we will have more precinct captains than at the beginning of the week.”

Meanwhile, even as Cain has said he will spend the next few days considering whether to continue his presidential run, his Iowa campaign is moving ahead full steam. The campaign now has 900 precinct captains. A new Cain TV ad begins running in Iowa today, while plans are being made for sending direct mail to Iowa voters.

Further hurting Cain is the fact that social conservatives seem to be moving away from seriously considering him as a candidate, complicating his efforts to run as the alternative to Mitt Romney. The Family Leader, a prominent social-conservative organization, announced last week that it had narrowed down its field of possible endorsees to Newt Gingrich, Rick Perry, Michele Bachmann, and Rick Santorum.

Meanwhile, Cain has dramatically fallen in the state polls, going from 23 percent in early November to 10 percent this week in polls done by Insider Advantage/Majority Opinion Research.

His announcement that he was considering ending his campaign compounded the damage done by White’s allegation, muses Robinson.

For those defending him, the “reassessing” comments were bound to be frustrating. “It wears people down,” Robinson says of the uncertainty.

— Katrina Trinko is an NRO reporter.