Former Maryland governor Martin O'Malley (D) made a little news on Sunday, using the tried-and-true tactic of underdogs in political history: Attack the front-runner.

The presidency of the United States is not some crown to be passed between two families,” O'Malley said ABC's "This Week." 

Whoever could he be talking about?

(AP Photo/Kevin Lamarque, Pool, File)

O'Malley's feistiness toward former secretary of state Hillary Clinton -- and, yes, Jeb Bush as well -- is a new character trait for the former governor. Prior to the "crown" comments, he had been decidedly quiet while Clinton labored through a brutal month as her exclusive use of a private e-mail server during her time at the State Department became a major topic of debate (and worry) among Democrats. O'Malley issued no statement on the revelations, and when offered a chance earlier this month on "Morning Joe" to hammer Clinton on the e-mail imbroglio, he offered up only the thinnest gruel. “Well sure, it would be important to me," he said of the idea of a public official using a public e-mail server. ZZZZZZ.

O'Malley's relative silence was interpreted as a sign that even if he did challenge Clinton in the 2016 Democratic primary, he would avoid trying to land the sort of body blows that could inflict real damage to the former secretary of state in a general election. O'Malley, knowing that his chances of winning were somewhere closer to none than slim, wouldn't blow up his chances at serving in a possible Clinton Cabinet by attacking Hillary, right?

That certainly appeared to be the mindset of some in Clintonworld. Witness comments made by former Michigan governor Jennifer Granholm, a strong Clinton supporter, on "This Week." (She appeared on a panel discussion after the O'Malley interview.)  “Martin O’Malley, he’s a very nice guy, and I was thinking that he might make a nice member of a President Clinton administration, so he better watch it,” Granholm "joked."

So, what's changed? Well, for one, O'Malley and his team quite clearly see an opening -- no matter how small -- caused by Clinton's unforced error on her e-mails. Ramping up the rhetoric is a probing attempt by O'Malley to see whether there really is a plausible path to beat -- or at least seriously challenge -- Clinton in a primary. Could a liberal's liberal without a famous last name have a chance -- if that person was willing to push (and push hard) the idea that Clinton represents an unnecessary compromise of ideals and an unnecessary continuation of the dynastic politics that people say they don't like?

The key to answering that question is another question: Just how far is O'Malley willing to go? Saying that the country shouldn't be governed by two families is a hit on Clinton, for sure, but it's neither the lowest of low blows (or anywhere close), nor is it, at least not yet, part of a sustained drumbeat by O'Malley on Clinton. The harder and further O'Malley is willing to go, the more risk he presents to the Clinton candidacy -- even if he can't ultimately beat her. (At the moment, it's hard to see him winning -- barring some large-scale unforeseen event or revelation.)

If O'Malley goes full political kamikaze, he could do Clinton genuine damage as she preps for the general election, providing Republicans with backup for ads that employ lines like "even Democrats like Martin O'Malley think it's time to move past the Clintons."

One episode of Clinton-bashing does not a trend make. But, it's hard to imagine that Granholm's reaction to O'Malley's critique landed very well in the former Maryland governor's camp. No matter what O'Malley does next, rhetorically speaking, when it comes to Clinton, she and her team would be very well-advised to avoid the "how dare you criticize us" and "you'll pay for it" lines of response.

So, what does O'Malley do -- or, more importantly, say -- next?  Does he retreat into talking generically about why he might be a better choice than the other Democratic alternatives? Or does he lean in to his Clinton criticism, endangering, maybe, his chances at a post in a Clinton Cabinet but making himself a far more relevant force in the coming primary fight?