DES MOINES — Voters in Iowa are notorious for not being willing to settle too early on any candidate. They use their influence as the state that goes first in the primary voting to vote to make sure they meet and greet and get a picture with every presidential hopeful before committing.

This time though they genuinely just can’t seem to make up their minds, and veteran party activists here say that this reluctance, particularly among the most conservative voters, to coalesce behind one candidate has created an unusually volatile race for the nomination. This is only heightened by the tendency among a crucial bloc of voters to shift drastically from one hopeful to another in a short period of time.

It seems that both former Massachusetts governor Mitt Romney and Rep. Ron Paul (R-Tex.) have small chunks of Iowa Republicans who will likely stick with them to the end.

But Republicans here say that any one of the five other candidates bunched in the polls — Rep. Michele Bachmann (R-Minn), businessman Herman Cain, former House Speaker Newt Gingrich, Texas Gov. Rick Perry and former senator Rick Santorum (Pa.) — could suddenly rally conservatives and win the caucuses Jan. 3.

Equally likely is that any of these five could also quickly loose momentum and fade altogether.

So far there is no evidence that Cain, who has been leading in some recent polls here, has lost any support in the wake of the sexual harassment allegations that have plagued him all week. But it would not be a huge surprise if that happened in coming days or weeks: Both Bachmann and Perry have surged ahead in the polls at different times only to quickly recede.

“I’ve never seen this level of undecided voters,” said Tim Albrecht, who worked on the Iowa campaigns of businessman Steve Forbes (2000) and Romney (2008).

“Usually, when you’re staring at November, you have a good sense of who will be in the top three on caucus night. As of now though, it’s anyone’s guess as to who will get their ticket punched out of Iowa,” added Albrecht, now the communications director for Iowa Gov. Terry Branstad.

The momentum shifts have been notable. “We’ve watched what’s happened in this race, Michele Bachmann caught fire and won (the straw poll), then Perry came in and he went ahead, so there’s been a lot of ups and downs, and that could happen two or three more times,” Branstad said.

Craig Robinson, a longtime GOP aide here who now runs a blog called the Iowa Republican, said that Iowa Republicans reflect the mood of the party nationally. While voters in Iowa get to see the candidates in person far more than in most states, the debates and national media coverage are also shaping their opinions. So they looked at Perry as a more electable alternative to Bachmann when he first entered, then abandoned him as he struggled in debates. But like Republicans nationally, they liked Cain after watching him win the Florida straw poll, so backed him instead of returning to Bachmann.

Now, in the wake of the Cain controversy, party strategists expect voters to give second looks to the other candidates, particularly Gingrich, who has not yet had a surge.

In interviews, conservative voters here say their careening from one candidate to another is natural, considering how the GOP race has unfolded. They describe several months in which candidates they might really like, from former Arkansas governor Mike Huckabee to New Jersey Gov. Chris Christie, flirted with runs but didn’t enter the contest.

Of the candidates who did enter, Republicans here say, they all have cast themselves as arch conservatives, but on close examination often have taken more liberal stands in their past.

“The thing with Santorum is why would he be with Specter,” said Jerry Van Wyk, a retired farmer who attended an event at a Baptist church in Marshalltown that featured Bachmann and Santorum. He was referring to Santorum’s decision in 2004 to back then-Sen. Arlen Specter (Pa.) in a Senate primary against Pat Toomey, who was the more conservative alternative and last year did win the seat from Specter.

On Perry, Van Wyk said, “I could vote for him today, but I’m not sure he would secure the border,” referring to the Texas governor’s policy of supporting reduced price, in-state tuition for illegal immigrants.

On Cain, Van Wyk said, “he says some careless things that make you wonder.” Van Wyk also wanted to learn more about sexual harassment allegations against the former Godfather’s Pizza executive.

And of Bachmann, he said, “ I prefer a man to be president, nothing against Michelle.”

One major shift has happened since 2008, Republicans here say. They argue that after the watching the rise of the tea party movement and the Republicans gains in Congress in 2010, it’s clear to them a consistent conservative can be elected president, without moving to the political center. At the same time, they are desperate enough to get rid of President Obama that they want to make sure the candidate is someone who can get elected.

And there is some desire to elect an outsider to Washington.

“We have a group of activists who are way down the field and candidates who are coming from another era and trying to catch onto where the base is,” said Steve Deace, a longtime conservative activist here who was a strong backer of Huckabee in 2008 but hasn’t found a candidate yet this time. “You latch onto a candidate and then you find something three or four months ago that you really don’t like and that makes you gun-shy.”

To many Republicans here, Romney long ago failed the conservatism test, with his support of abortion rights and health care reform in Massachusetts. And they say Perry’s campaign has raised doubts about his conservatism, while they worry Bachmann is too polarizing to win against Obama.

Cain’s outsider status seems to have lifted him above Gingrich and Santorum for now.

Julie Roe, a conservative in a rural Hardin County, Iowa, said she had watched closely earlier in the year to see if Huckabee or Rep. Mike Pence (R-Ind.), another favorite of social conservatives, would enter the race as an alternative to Romney. She considered Bachmann, but on the eve of the Ames straw poll in August opted for former governor Tim Pawlenty (Minn.) based on his executive experience.

But that pick was a reluctant one: She worried Pawlenty, despite his attacks on Romney earlier in the race, might drop out and then endorse the former Massachusetts governor. That concern was well-founded; Pawlenty did eventually endorse Romney.

“I am resigned to support in the Iowa caucuses whoever is best poised to topple Romney. I will look at the dynamics of the current field the week before caucus and vote for the un-Romney,” she said. “The field that remains is acceptable if not exciting, each candidate with their own problems.”