Maine's biggest city picked a new mayor this week, leaving the rest of us left to wonder how and why.

Not that there are questions about the winner, Portland City Councillor Nick Mavodones. He's had the job before, and remains popular with his colleagues and the public, running without opposition for an at-large council seat earlier this month. If there were city-wide elections for mayor, Mavodones would be on a short list of candidates who could win.

But since Mavodones was selected unanimously Monday without two minutes of public discussion, we can only guess what attributes won him the job.

For Portland residents who are still on the fence about whether the city should have an elected mayor, this transition should provide food for thought. Not because the wrong person was picked, but because the way he was picked remains something of a mystery.

Mavodones is a Democrat, and although the council is nonpartisan, Democrats have five of the nine seats and the ability to decide most issues. It makes sense that a Democrat is mayor, but why this Democrat? What process was used to decide? Those questions take away from his stature when he represents the city.

If there had been an election, Mavodones would have run on a platform and would come into office with an agenda. Instead he follows in a long line of Portland mayors whose main duty is pounding a gavel at council meetings. We can guess that his agenda will be dealing with another year of the city's financial crisis, but an election would have required him at least to say how.

The mayoral selection process has some bright spots, however. The council has dropped what had been described as a tradition of picking the most senior council member who hadn't had the job before.

For the last two years, that would have been Kevin Donoghue or David Marshall, two members of the Green Independent Party. Both are able councilors with lots of good ideas and could make good mayors.

But the job is too important for people to take turns at it. Even a vote of five councilors is better than no vote at all. It would be much better still if we knew why he got the votes.