This points to the first part of O’Malley’s double-bind. Clinton’s dominance when it comes to endorsements, campaign cash and press attention means that the only way to beat her is as an insurgent. But Sanders, a genuine political radical who has thrived outside the traditional party structure, is far better suited to this role than O’Malley, who sports the résumé of a more conventional political climber. Sanders’ four-decade political career amounts to a purist’s crusade against inequality, wealth concentration and corporate power, lending him credibility with the true believers of the left that’s virtually impossible to match. So while O’Malley and Sanders now occupy much of the same ideological turf, it’s only Sanders who is generating excitement with the base. 

A much more comfortable role for O’Malley would be as a candidate of the establishment — someone who appeals to the party’s powerful and pragmatic leaders, who are more interested in backing and gaining influence with a winner. With his solid credentials (two terms leading a major state and two more running one of the country’s largest cities) and connections with elected officials, donors and interest group leaders, O’Malley would have a shot at playing this role in a different field. But Clinton’s presence makes it impossible right now. She’s locking down more support than any non-incumbent frontrunner before her. There’s just not room for another candidate of the establishment.