Martin O’Malley remembers running for president like this: He is on a train, heading for a bridge. He can see the bridge is giving out. He is shouting and waving and pointing at a “better lane,” he says. “But it’s like I couldn’t get anybody on the train to listen.”

“It was the most frustrating experience I’ve ever had in politics.”

O'Malley was still a young mayor in Baltimore, elected at 36, when he started hearing people say he might one day “go all the way.” Now, at 54, on the other side of that dream, he is at turns resigned to and not yet at peace with the eight months he spent as a candidate for the Democratic nomination. That his 2016 campaign never caught fire, or even much of a spark, is a reality he reasons with in one moment, ticking off outside contributing factors, before adding in the next that, in fact, “None of it made sense.”

“I couldn't not try,” he says in a recent interview over two rounds of Guinness and plantain chips at a Cuban restaurant in Baltimore, the city where he launched his career. “But at the same time it was very frustrating,” he adds. “Really, really frustrating.”

“Thank God I picked the right high office to have that experience.”

It was around this time four years ago that O'Malley, the former governor of Maryland, began erecting the “framework” for his presidential bid. And now, like then, he is filling his calendar with party work, helping candidates in special elections (two in Iowa, one in Delaware), and headlining local fundraisers and events (most recently, last weekend, in Iowa). And now, like then, he is toying with the idea of a campaign. (“As for the question of whether I might run for president again in 2020, I just might," he told NBC News.)

But this is not the O’Malley who ran headlong into 2016. More than a year after his dismal finish in Iowa, securing less than 1% in the caucuses against Hillary Clinton and Bernie Sanders, he still carries the frustration of a campaign spent trying and failing to find an “option to open up the lane.” He has a new distaste for the party establishment (“Washington gobbledygook”). And even as he supports local Democrats, trying to carve out his own role as the party centers itself around President Trump, he is without a clear next move for the first time in years.

His hard-charging political operation — a tight cadre of advisers, one or two always by his side in the years before 2016 — is no longer a familiar presence. He travels now with a single aide, a young operative named Ben Chou who ran the campaign's operations team in Iowa. As the only full-time staffer at O'Malley's PAC, O'Say Can You See, Chou helps manage the political work and keep an eye on the budget. (They began their trip to Iowa last weekend on the east coast around 5 a.m., touched down in Des Moines for a full day of events, before turning promptly around the next morning on a 7 a.m. flight.)

O'Malley has made himself widely available as a surrogate, telling officials at the Democratic committees in Washington that he is willing to go anywhere that's helpful.

Mostly, though, he is home with his family in Baltimore or at Boston College Law School, where he teaches a course on the data-driven government and "performance management." The practice of using data to evaluate government and dictate policy is one that O’Malley pioneered as mayor and governor and has described as central to what he once called his “omni-partisan, apolitical” and “not fundamentally ideological” governing philosophy.

Despite a brief effort by aides in 2013 to promote O’Malley as a “performance-driven progressive” with a “brand of results-oriented leadership,” these ideas didn’t become central to his campaign. (Perhaps in part because the tough-on-crime policies and tracking programs that put him on the cover of Esquire as “America’s best young mayor” in 2002 would in 2016 alienate the young voters who have protested the police tactics and sentencing policies that produced one of the world’s largest prison populations.)

Instead, O’Malley launched his campaign under the banner of a “New Leadership” slogan; made an aggressive play to be the most progressive candidate in the race; and became sharply critical of Clinton, a candidate whom he endorsed and campaigned for at length eight years earlier.

As he sees it — and this remains a going topic of discussion — his problems were more structural. First, there was money. (The Clintons were “formidable,” he says, in “shutting down fundraising potential.”) Second, a climate of “discontent” on which Sanders, he says, had a “monopoly.” And third, the debates. (With only four before the Iowa caucuses, he says, an “unknown” candidate had no chance of “breaking through.”)

His refrain about deciding to run in 2016 despite improbable odds — “I couldn’t not try” — is one he seems to offer less as an explanation than a hard statement of fact.

Supporters at an event in Iowa last weekend were unsure whether to laugh when, after thanking them, O’Malley added flatly: "Seeing as how things turned out [with Trump], I want to thank you for saving my life, because I'd probably be suicidal if I hadn't tried.”

The remark, if not literal, was serious — an urge rooted in part in what friends have described as a genuine belief, affirmed by others along the way, that he could do the job. (It was Bill Clinton, in 2002, who wrote to say, “I won’t be surprised if you go all the way.”)