Democratic presidential candidate and former Maryland governor Martin O'Malley arrives at a forum at First Christian Church on Jan. 9 in Des Moines. (Bryon Houlgrave/AP)

— In the upcoming Iowa caucuses, the second choice of Martin O’Malley supporters could matter far more than the first.

Despite spending more time in the state than either of his Democratic rivals, the former Maryland governor remains mired in the single digits in polling, and under the complicated rules that govern the first-in-the nation caucuses, that’s a real problem.

In most of the state’s 1,681 precincts, candidates must win 15 percent of the votes or their performance is recorded as zero. At that point, the candidate’s supporters are free to move to another hopeful who is considered viable.

Come Feb. 1, that could prove a real boon to either former secretary of state Hillary Clinton or Sen. Bernie Sanders (Vt.), who are locked in a tight race that will go a long way toward shaping the rest of the Democratic race.

“It could be a game changer,” said Scott Brennan, a former chairman of the Iowa Democratic Party. But which way O’Malley supporters might go remains “the million-dollar question at this point,” he said.

Democratic presidential candidate, former Maryland Gov. Martin O'Malley, right, poses for a selfie with an attendee after speaking at a town hall at Grinnell College in Grinnell, Iowa, Wednesday. (Patrick Semansky/AP)

On the one hand, O’Malley was among the first governors in the nation to endorse Clinton for president when she ran in 2008. He got a taste of politicking in the early nominating states that cycle by serving as a surrogate for the future secretary of state.

“I would assume more of the O’Malley supporters would join the Clinton group,” said Tom Henderson, the longtime Democratic chairman in Polk County, the state’s largest jurisdiction, who is backing O’Malley.

On the other hand, some of O’Malley’s rhetoric in the 2016 cycle — including calls to break up the big banks and address income inequality — has sounded more like Sanders than Clinton.

“He’s kind of a new face, so I would think those folks would break more than 50 percent toward Senator Sanders,” Brennan said.

O’Malley’s campaign team, which continues to suggest he’ll prove surprisingly strong on caucus night, isn’t playing the speculation game. Other observers say it’s likely O’Malley will hit the 15 percent threshold in some precincts, where there are pockets of greater support for a candidate who hasn’t managed to get much traction in statewide polling. His campaign has been most visible in larger cities such as Des Moines and Cedar Rapids.

In the latest Des Moines Register-Bloomberg Politics poll — considered the gold standard of Iowa caucus polling — Clinton led Sanders by just two percentage points, 42 percent to 40 percent. O’Malley lagged far behind with 4 percent.

The Fix's Chris Cillizza previews the Iowa caucuses, looking at what the outcome could mean for both Democrats and Republicans. (Peter Stevenson/The Washington Post)

Given how close Clinton and Sanders are, the second choice of O’Malley supporters “could move things a couple of percentage points,” said Dave Nagle, a former congressman and former chairman of the Iowa Democratic Party. “That could have a huge impact.”

Aside from ideology, O’Malley supporters could also be lured to the Clinton or Sanders camps based on long-standing personal relationships or the personalities of their respective precinct captains, Nagle said.

All sorts of gamesmanship has been known to take place in the Iowa caucuses, which operate very differently from presidential primaries.

Iowans must show up at an appointed hour at their local caucus site, which could be a school, library or living room. There are no secret ballots. Participants instead move with fellow supporters to one side of the room to demonstrate their support.

In one celebrated case in 2004, two candidates — former senator John Edwards of North Carolina and former congressman Dennis J. Kucinich of Ohio — cut a deal, under which they agreed to back the other in precincts where one of them was not viable.

The arrangement factored into a strong second-place finish that year by Edwards, whose Iowa performance propelled him in what later became a ­two-candidate race for the nomination with then-Sen. John F. Kerry of Massachusetts.

Operatives in the Clinton and Sanders camps said no such formal deal is in the works this time around. But aides to both candidates said there is more subtle outreach going on to O’Malley supporters.

Organizers for both Clinton and Sanders said they routinely ask likely caucus-goers who their second choice is and will come armed with that knowledge on caucus night.

Other forces will be at work as well. The way caucuses work, candidates are trying to accumulate delegates, which are awarded based on the relative strength of their showing in each precinct.

But there are a limited number of delegates available to be awarded at each site. That can create a situation in which the leading candidate might be willing to give up some supporters to improve the standing of a rival candidate.

Why would someone do that? In this year’s case, it’s possible, for example, that Sanders could direct some of his supporters to join O’Malley in a given precinct and, in doing so, deny Clinton a delegate there. That would boost O’Malley’s total but make it more likely that Sanders prevails statewide over Clinton.

Beverly Strayhall, a longtime Democratic activist in the Waterloo area who is precinct captain for O’Malley, said she’ll be willing to cut deals with either the Clinton or Sanders camp if it improves the standing of her preferred candidate.

“On caucus night, my job is to maximize his chances of getting Martin O’Malley delegates,” Stray­hall said. “I know it sounds terrible, but if I’m there for Martin O’Malley, I want to figure out how to make him viable.”

If O’Malley were to fall short of that threshold in her precinct, Strayhall said, she’s not sure whether she would back Clinton or Sanders — or stay on the sidelines.

“I’m not hearing compelling arguments either way,” she said.