The two former governors had banked on a strong showing in the Hawkeye State to buoy their candidacies, but failed to gain traction against better-funded operations and an election season marked by voter desire for anti-establishment candidates.
"This fight continues," O'Malley said at a rally in Des Moines, Iowa. "We fought very, very hard in order to give the people a choice, and the people made their choice tonight."
The former Maryland governor used his speech to push for greater gun control, action to address climate change, equal pay for women and other efforts to address income inequality. He expressed gratitude to his supporters and the people of Iowa, but took a moment to denounce the "racist and fascist rhetoric of Donald Trump."
"We have to hold strong to the values that make us Americans," said O'Malley as his family stood by his side. "And that, too, was what this tough fight was about."
O'Malley did not endorse a candidate as Hillary Clinton and Bernie Sanders were locked in a virtual tie in the first-in-the-nation voting state.
O'Malley entered the race on May 30, but never cracked double-digits in national polls and struggled to gain traction with more liberal voters as Sanders, a self-described democratic socialist, emerged as Clinton's leading challenger.
Despite the poll numbers, O'Malley competed aggressively in Iowa and New Hampshire, pushing the Democratic National Committee to add debates. He had staked a strong showing in Iowa to fuel his candidacy, which was focused on being an alternative to Clinton. He crisscrossed the state seeking support
but was unable to establish a strong foothold before Sanders came in and rallied liberal and young Democrats around his candidacy.
Huckabee's exit unplanned
Huckabee, meanwhile, the winner of the 2008 Iowa caucuses, thanked his supporters on Twitter.
"I am officially suspending my campaign," the former Arkansas governor tweeted. "Thank you for all your loyal support. #ImWithHucK"
Huckabee's decision to suspend the campaign was not planned, but after seeing the results he decided it was best to step out of the race.
"He is going to continue to push for the issues he believes, but right now this is about thanking his staff and supporters and being with his friends and families and see what doors will open next," said Hogan Gidley, Huckabee's spokesman.
A 60-year-old Southern Baptist minister, Huckabee first entered office in 1993, when he won a special election for lieutenant governor of Arkansas -- a job that opened up as part of the domino effect of Arkansas Gov. Bill Clinton being elected president.
He became governor in 1996, when Clinton's former lieutenant governor Jim Guy Tucker was convicted as part of the Whitewater controversy. He was elected to four-year terms of his own in 1998 and again in 2002.
After Huckabee's 2008 presidential campaign sputtered out despite his win in Iowa, Huckabee joined Fox News and hosted a weekend program. He passed on another campaign in 2012, and left Fox News early in 2015.
His 2016 campaign -- much like another former Iowa caucuses winner, former Pennsylvania senator and 2012 victor Rick Santorum -- encountered two insurmountable forces: Trump and Texas Sen. Ted Cruz.
Trump upended the GOP campaign and pulled in populists who had previously been attracted to Huckabee's stances on trade deals and his opposition to changes to entitlement programs like Social Security. Cruz, meanwhile, pried away Huckabee's support among evangelical voters.
He attracted his share of controversy during his 2016 bid -- most notably by denouncing President Barack Obama's Iran nuclear deal by declaring, in a reference to the Holocaust, that Obama "will take the Israelis and march them to the door of the oven."