It's called Instant Runoff Voting, and it will allow (but not require) voters to mark not only their first choice for Town Council seats but second and third choices as well. So voters should come prepared with opinions about candidates other than their favorite in three-person races.

Although many "alternative" voting methods are used around the world, and esoteric arguments abound about which best reflects the will of the electorate, Instant Runoff Voting is being touted in Cary mainly as a way to save money. It eliminates the need for a fairly costly ($62,000 or so) runoff election in November if no first-round majority winner emerges in one or more races. Such runoffs are notorious for low voter turnouts, in single-digit territory.

Instead, on Tuesday there will be two elections for the price of one, if need be.

If, in any race with more than two candidates, no candidate wins a majority of first-choice votes, some voters' second and third choices will be taken into account.

Here's how: The two candidates with the most first-preference votes "enter" the Instant Runoff. All other candidates are eliminated. The ballots on which those eliminated candidates had been ranked first are reviewed, and those voters' second and third choice votes are tallied. From each ballot a vote goes to whichever finalist is ranked higher. The finalist with the most overall votes (his or her first-round votes, plus the added preference votes) wins.

Got it?

The point Instant Runoff proponents stress is that designating a second or third choice will not harm your first choice's chances. All it will do is give you a say in the runoff if your candidate doesn't finish in the top two.

Those are valid points. And, under this system (being tried also in Hendersonville), the victors are likely to win with higher vote totals than they would get in a sparsely attended November runoff. Score one for democracy.

That said, there are a couple of additional factors Cary voters need to consider. One is that only two races are in the running for Instant Runoff treatment, the council seats in District B and District D. Each has three candidates for one seat. (There are four names on the ballot for an at-large council seat, but two candidates, Susan Lawson and Roger Hill, have officially withdrawn.)

So voters in Districts B and D will want to do their homework. (The N&O's voter guide, which has been available online, is scheduled for inclusion with the newspaper today.)

Factor Two is that, at least this time, Instant Runoff won't be instant. If there is no first-round majority winner, the backup votes will have to be hand-counted, because preference-tallying software for the voting machines isn't available.

Here's hoping Cary's experiment will add interest -- and minimal confusion -- to Election Day.