Just not in the way he had hoped.

In the final Des Moines Register/Bloomberg Politics poll before the Iowa caucuses, O'Malley sat at 3% support, within the 4-percentage-point margin of error. But that's also the exact spread between Hillary Clinton and Sen. Bernie Sanders -- making O'Malley's voters potential difference-makers Monday night.

Here's why: Democratic Iowa caucus rules say that to reach "viability," a candidate must have support of 15% of the caucus-goers in that precinct. If too few voters support a candidate, those individuals are freed to support another candidate of their choosing.

While O'Malley's core support is small, those backing him tend to be committed caucus-goers who understand the process, would never skip it and know how to cut deals, several Democratic strategists said.

And the Clinton and Sanders camps have each made a point of identifying O'Malley's backers and persistently reaching out in an effort to become their second choice.

It's in part an effort by Clinton to reverse a mistake of her 2008 campaign. Then-Illinois Sen. Barack Obama identified supporters of lower-polling candidates like Chris Dodd and Joe Biden and courted them heavily, while Clinton's campaign purged other candidates' supporters from its contact lists.

Right now, O'Malley is telling his voters to "hold strong," imploring them on social media, national television and in person to stick with him -- at least at first.

"Hold strong in that first alignment," O'Malley told volunteers gathered at a phone bank at his precinct captain's home in Boone, Iowa, Saturday evening. "I need you."

He said Iowans have a tendency to pick new leadership, and preached optimism that he could be that choice.

"We have to beat expectations," O'Malley told reporters. "I'm hoping and working to make my campaign the surprise that comes out of Iowa."

If the race is a nail-biter, the O'Malley voters could be particularly influential in precincts with odd numbers of delegates -- 11, rather than 10, for example -- because they could tip what looks like a tie into a one-delegate victory there.

"In a tight race, as someone starts getting the edge on that second choice pick, it could make all the difference in the world," said Brad Anderson, a Democratic strategist who led Obama's re-election effort in Iowa in 2012.

The Clinton campaign even has an app for volunteers to count the number of supporters for each candidate and send caucusers to O'Malley's side if it keeps Sanders from winning an extra delegate.

Clinton or Sanders?

There's no sign at the moment that O'Malley is prepared to cut any sort of deal with another candidate.

John Edwards and Dennis Kucinich did so in 2004: Each asked the other's supporters to back whichever candidate was viable in their precincts, helping to propel Edwards to a second-place finish.

O'Malley's voters, many experienced caucus-goers, know what they're getting into.

His precinct captain, Pam Nystrom, who hosted the phone bank Saturday night, said she is doing her best to get enough voters to push O'Malley over the threshold.

But she says if they can't, she'll vote for Sanders. So will her husband, Marck Nystrom, a retired school administrator like his wife.

In fact, every O'Malley supporter of the small group gathered in Boone, described by Nystrom as a progressive, blue-collar district, said Sanders was their second choice.

"I'll go Sanders in a heartbeat," said Lewis Stahl, a retired employee of the Union Pacific Railroad, who will caucus in Ogden, Iowa. He spoke forcefully against the "machinations" of the big-money in New York and Democratic Party that he sees as supporting Clinton.

In The Des Moines Register poll, Sanders and Clinton were essentially tied as second choices: 26% for Clinton and 28% for Sanders.

John Vilmain and his wife, Linda, were more favorable toward Clinton, but still had Sanders second.

Both John Vilmain and Stahl said they fully expect the other campaigns to come after their vote, with Stahl saying he can't keep up with the mailings from Sanders and Clinton.

"The minute you're not viable, you're as popular as honey on a biscuit," Vilmain said of caucus night.