The former Maryland governor also said Clinton's path to the Democratic nomination seemed "no longer quite so inevitable," and that voters want clarity from their politicians rather than the "triangulation" politics of the first Clinton administration.
Clinton said Sunday that the U.S. should accept 65,000 of the millions of Syrians who have been displaced by that country's civil war. O'Malley made the same argument, citing the same number, in early September.
"It's kind of the pattern of this campaign: We lead, and she follows public opinion polls," O'Malley said in an interview with The Baltimore Sun. "I believe there's a big difference between forging a new consensus and putting your finger to the wind."
O'Malley's early support for resettling Syrians in the U.S. not only reflects his efforts to be a leading voice on immigration and refugee issues — he drew national attention last year for opposing the deportation of Central American children — but also efforts to garner attention for his fledgling campaign.
O'Malley can be at the forefront of proposing new policies and ideas on controversial issues in part because he has so little to lose. The two-term governor and former Baltimore mayor is polling at around 4 percent in Iowa and 1 percent in New Hampshire, despite months of aggressive campaigning.
The Democrat has weighed in first on a range of high-profile matters, offering detailed policy proposals on Wall Street regulations and student debt, for instance. While Clinton announced her opposition to the Keystone XL oil pipeline on Tuesday, O'Malley said he was against it back in November.
Several observers agreed that O'Malley has beaten both Clinton and Vermont Sen. Bernie Sanders to the punch on some issues. The question for O'Malley, they said, is whether anyone is noticing.
"For whatever reason, he's been left out of the media mix," said Democratic strategist Brad Bannon. "Very few Democrats out there know he exists."
But, Bannon said, raising the issues is smart strategy, particularly as Clinton's campaign has shown signs of vulnerability. "There are a lot of Democrats out there who are floating, looking for an alternative," he said.
Millions of Syrians have been displaced by the ongoing conflict against the Assad regime and Islamic State fighters, creating the largest migration crisis in Europe since World War II. The Obama administration has committed to accept 10,000 refugees from Syria in the next fiscal year.
O'Malley has argued that that number is not adequate. On Sept. 4, he called on the U.S. to resettle 65,000 Syrians, a figure suggested by the United Nations and humanitarian groups such as the International Rescue Committee.
"We have to step up here," O'Malley said Wednesday. "Don't think for a second that this doesn't affect our credibility and our effectiveness in the eyes of the other people of this world."
Clinton made a similar argument Sunday.
"I think the United States has to do more," Clinton said on CBS' "Face the Nation." "I would like to see us move from what is a good start with 10,000 to 65,000 and begin immediately to put into place the mechanisms for vetting the people that we would take in."
The Clinton campaign did not respond Wednesday to O'Malley's comments.
Sanders, who has been gaining on Clinton in his bid for the nomination, has not said how many Syrians he believes the U.S. should accept.
Before launching his campaign for president, O'Malley enjoyed close ties to the Clinton family. President Bill Clinton appeared in a television ad for O'Malley's 2006 campaign for governor. O'Malley, in turn, was an early supporter of Hillary Clinton's 2008 presidential campaign against Barack Obama.
But O'Malley has shown a willingness to break with both Clinton and Obama. He did so during an earlier refugee crisis by publicly criticizing the White House for attempting to expedite the removal of child immigrants from Central America who were streaming across the border last year.
"We are not a country that should turn children away and send them back to certain death," O'Malley said at the time.
The comments drew praise from immigrant rights groups but opened a rift with the White House. News leaked that the governor was trying to wave federal officials off a potential shelter for the immigrants in Carroll County at the same time he was condemning the Obama administration.
O'Malley acknowledged that effort but said he wanted the children placed with families or in small settings rather than in an institution.
More than 5,100 children ultimately were placed in Maryland, a higher share per capita than any other state. The children were placed in Maryland because of the state's high concentration of Central American families, not because of anything O'Malley's administration did. Still, those involved with the effort gave O'Malley high marks for his response as governor.
William J. McCarthy, Jr., executive director of Catholic Charities of Baltimore, said the state had limited power to address the influx of children, but that O'Malley deserved credit for bringing private service organizations together to coordinate their care.
"The governor and the administration were very clear … that government alone couldn't fix this problem," said McCarthy, whose group was closely involved in the effort. "But Maryland, much more than other states, really responded to that crisis in a somewhat heroic way."