O’Malley is the second-term Maryland governor who has been perhaps the most open about his 2016 ambitions, but whose prospects are largely out of his hands as long as Clinton looms on the horizon. Count New York Gov. Andrew Cuomo, Delaware Gov. Jack Markell, Missouri Gov. Jay Nixon, Massachusetts Gov. Deval Patrick, Vermont Gov. Peter Shumlin and Hickenlooper himself on that same roster of accomplished Democratic governors who are younger than the 65-year-old Clinton but could find themselves stuck in their state capitals for another decade-plus should she be elected president.

It’s an unprecedented scenario, noted some of the governors: a first lady-turned-senator-turned-presidential candidate-turned Secretary of State with 100-percent name ID and deep popularity who would, oh yes, make history as the nation’s first female president.

Even the most impressive health care delivery reforms and far-reaching gun control restrictions pale by comparison.

“It’s just a very unique situation in which an extremely qualified candidate with a long history of public service who has been fully vetted is considering running for the presidency,” noted Nixon, who easily won reelection last year to his second term in conservative-leaning Missouri. “She’s entitled to her time of analysis. It does, I think, in many ways freeze the field until she more clearly states what she wants to do with the rest of her life.”