If the number of people interested in running for the newly expanded job of mayor of Portland continues to grow, there may be more candidates in the race than there are voters trying to decide among them.

OK, that’s an exaggeration. But few people predicted, when the city’s charter was changed last year to incorporate an elected mayor with somewhat expanded duties and a salary of $66,000, that the number of people taking out papers for the job would be running into double digits by the middle of the summer.

And there’s still nearly two months to go before petition signatures must be turned in. With the number of eligible signatures required to get on the ballot at the low figure of 300 to 500 voters, the odds are that the candidate list will get even longer before the Aug. 29 deadline.

Right now, 16 contenders have registered to collect signatures, with one additional hopeful, a local firefighter, declared ineligible due to a rule barring city workers from running.

The situation is made even more complicated by another charter change that implements, for the first time in Portland, a system of weighted voting that asks people to mark their ballots for their second and subsequent choices. With perhaps two dozen or more candidates, that almost certainly guarantees that no single one will get a first-round majority.

Officials will have to total up second-, third- or even lower-place preferences before coming up with 50 percent plus one to elect a new mayor.

Voters should now be realizing just what kind of a burden they have placed on themselves. If they are going to make intelligent, informed decisions about the candidates, it’s not enough to know the one they like the best.

They may have to pick out of a very large field the top two or three or five (or more) people whom they believe will do the best job leading the city for the next four years.

The odds are that only a small minority of voters will see their first choice settle into the new mayor’s expanded job when 2012 rolls around. Many more will see someone they did not believe would do the best job being selected as the person to do it. True, that would also happen without ranked-choice voting, but the new system lets more people influence the final outcome — whether they care about their other choices or not.

Thus, there will likely be a lot of hard swallowing behind the voting-booth curtain when November rolls around.