In particular, the US needed a leader willing to "take on powerful, wealthy special interests". Whether he meant corporate behemoths like Wall Street and Big Oil, or Bush and Clinton, was not clear.
It's also not clear if O'Malley, who served as Baltimore's mayor from 1999 to 2007, when he began a two-term tenure as Maryland's governor, is the man for the job.
A liberal Democrat who relaxes by playing guitar in a band, O'Malley cut his political teeth as a staffer on Gary Hart's two doomed presidential campaigns. His gubernatorial highlights include legalising gay marriage, raising the minimum wage, abolishing the death penalty and legislation to protect Chesapeake Bay.
He favours resurrecting the Glass-Steagall Act, dumped by Bill Clinton, to rein in banks. He would also allow illegal immigrants to apply for driver's licences. Both are opposed by Hillary Clinton.
But O'Malley's public profile is near zero. He remains a long-shot underdog, polling between 1 and 2 per cent nationally. Despite spending hundreds of thousands of dollars, including US$45,000 ($60,000) donated to Iowa Democrats, to support his party in the 2014 midterms, essential strategy to build regional support for any presidential run, a recent Iowa poll [the Iowa primary is a vital way station to the White House] placed him at 0 per cent.
In contrast, a CNN poll found 62 per cent of Democrats favoured Clinton as their candidate. In Iowa 55 per cent of Democrats felt this way.
Does O'Malley have any shot at beating the Clinton juggernaut? He told CNN he planned to "go from county to county, from town to town and engage people in order to change that around". In short, join other candidates on the campaign trail.
The "inevitable frontrunner" - read Clinton - said O'Malley "is inevitable right up until he or she is no longer inevitable".
Does he have the right stuff? "Well, he looks good," laughs Larry Sabato, director of the University of Virginia's Centre for Politics. "The Daily Iowan called him 'an echo of John F. Kennedy'. Every four years Democrats look for John F. Kennedy. Just like Republicans look for Ronald Reagan."
Looks aside, Sabato notes O'Malley was "massively unpopular" after eight years as governor, when he raised taxes and was dogged by corruption within his administration. "Not only is he is unknown. But the best known fact about him is that he managed to lose the governorship of Maryland, which is one of the five most Democratic states."
O'Malley's hand-chosen successor was wiped out by the Republican candidate, a very public snub.
Nonetheless, O'Malley's comments underscore that Clinton's political machine may be vulnerable. Certainly, her support groups were quick to pounce on O'Malley, stressing Clinton had "worked her entire life" for "working- and middle-class Americans".
If O'Malley declares, and survives to contest the primaries, he might, just, push Clinton's position leftwards. This means voicing his party's doubts about Clinton - she represents more of the same, not real change - by exploiting the dynastic card.
"Somebody's going to collect the percentage of Democratic voters who won't vote for Hillary Clinton," says Sabato. "The question is, is O'Malley the only serious candidate on the ballot opposite Hillary? Or does Jim Webb run? Does Bernie Sanders run? Do others run? Then the vote will be split. I don't know of anybody who seriously believes O'Malley will be the nominee."
Until O'Malley, 52, stepped up, playing to the party's left in Iowa last week, party progressives coalesced behind Elizabeth Warren, the Massachusetts senator and economic populist. With Warren insisting she will not run for president, Sanders became the left's champion, raising issues like inequality. His age, 73, makes him a long shot. A younger left-wing populist, able to connect with voters, may give Clinton, 67, a run for her money.
O'Malley's dynastic jibe strikes a chord. Many wonder if meritocracy has taken a back seat in US politics.
"There is deep dissatisfaction with the prospect of another Clinton-Bush race," says Sabato. "And more of it, frankly, is focused on Bush. He would be the third Bush [father George Herbert was 41st, brother George Walker was 43rd and Bill Clinton was 42nd] from that small, immediate family in three decades. There's something un-American about it, frankly. We look like a banana republic."
Is a Bush-Clinton showdown inevitable? "I think Clinton's likely to be the Democratic nominee. I'm much less certain about Bush."
So is his party. Sabato notes a "deep wellspring of anti-Bush feeling" among Republicans.
Hardly surprising in a party, made more populist by the Tea Party, riven by internecine warfare.
Senator Marco Rubio and Governor Scott Walker are mainstream prospects. But Jeb Bush boasts a formidable family machine with deep pockets.
While O'Malley woos Warren's fans, tacking left as he talks up holding banks and Wall Street to account, Team Clinton will not buckle to dynastic talk.
But O'Malley's move, plus the likelihood many Republicans will declare in coming weeks, puts pressure on Clinton to make a move.
Her rivals face a potent "it's our turn" sentiment; that now a black man has occupied the White House, a woman should be next.
"That is the hidden, giant card Hillary's got," says Sabato. "It's going to be the new, 'It's the Economy Stupid'." That worked for Bill in '92. Hillary must be praying Warren doesn't change her mind.
