Martin O'Malley: What really is his Wall St. agenda?

Former Maryland Governor Martin O'Malley announces his intention to seek the Democratic presidential nomination in Baltimore, May 30, 2015.
Jim Bourg | Reuters
Former Maryland Governor Martin O'Malley announces his intention to seek the Democratic presidential nomination in Baltimore, May 30, 2015.

Former Baltimore Mayor and Maryland Gov. Martin O'Malley is basing his presidential campaign in large part on hammering the excesses of Wall Street, calling out Goldman Sachs CEO Lloyd Blankfein specifically and saying both Hillary Clinton and Jeb Bush are too close to the titans of high finance.

"Goldman Sachs is one of the biggest repeat-offending investment banks in America. Recently, the CEO of Goldman Sachs let his employees know that he'd be just fine with either Bush or Clinton," O'Malley thundered in his announcement speech. "I bet he would. Well, I've got news for the bullies of Wall Street—the presidency is not a crown to be passed back and forth by you between two royal families."

O'Malley kept up the heat in appearances on ABC over the weekend and on Monday. He told host George Stephanopoulos: "I believe that the presidency is a sacred trust, and I believe that we are best served by giving the choice of who our president should be to the people of the United States and not to the big banks on Wall Street."

Read MoreDespite GDP, economy works in Hillary's favor

But a source tells me that in November 2013, O'Malley schmoozed with some of those Wall Street bullies in a private dining room at Lever House, a fancy restaurant in Midtown Manhattan.

The guest list, according to the source, included Robert Wolf, a top Wall Street supporter of President Barack Obama (who now is supporting Hillary Clinton for president), Marvin Rosen, a Wall Street attorney and at least one Goldman Sachs executive. The event was a meet and greet and not a fundraiser, O'Malley's staff points out. But you generally don't sit down with Wall Street political rainmakers without hope of eventually wringing big checks out of them.

Critics of O'Malley's recent populist approach also note that he penned an op-ed for the Washington Post in 2007 with former U.S. Rep. from Tennessee and current Morgan Stanley executive Harold Ford Jr. calling for Democrats to heed the "vital center" and praising the moderate views and approach of former President Bill Clinton, who signed the law that tore down the Glass-Steagall wall between investment and consumer banking and paved the way for the creation of today's financial super-market mega banks.

"As the caucuses and primaries approach, candidates will come under increasing pressure to ignore the broader electorate and appeal to the party faithful," O'Malley wrote at the time, summing up exactly what he himself is trying to do in 2015. "But the opportunity to build a historic majority is too great—and too rare—to pass up."

While he praised Bill Clinton at the time, O'Malley is now calling for the breakup of the nation's largest banks and re-imposition of the Glass-Steagall wall.

O'Malley spokesperson Haley Morris said of the 2013 Wall Street event: "He has dinner with lots of people, some he agrees with, some he doesn't. His stance on Wall Street is pretty clear cut, and if anything this would prove his independence."

And O'Malley supporters note that he has a clear progressive record on health care, immigration and other issues while downplaying his former affiliation with the centrist—and now defunct—Democratic Leadership Council.

Read MoreObama faces much bigger trade fight in the House

Still, O'Malley's past may make it difficult for him to take up the pitchfork against Hillary Clinton, especially with self-proclaimed socialist Bernie Sanders in the race and gaining momentum in Iowa.

The O'Malley theory of the case is that Sanders is currently filling a void with Sen. Elizabeth Warren, Democrat of Massachusetts, officially out of the race but that the rumpled Vermont independent will eventually fade when people realize he could never win a national election.

Then O'Malley could be poised to occupy the "Not Hillary" spot as a more palatable general election possibility. The odds, of course, are very strong that no one will give Clinton much of a scare for the nomination. But O'Malley's past centrist views and Wall Street hobnobbing may make it especially challenging for him to gain significant traction.

—Ben White is Politico's chief economic correspondent and a CNBC contributor. He also authors the daily tip sheet Politico Morning Money [politico.com/morningmoney]. Follow him on Twitter @morningmoneyben.