A good idea being touted by several of Minnesota's "third" parties is still a good idea, even though those parties failed to score any world-shocking victories in last week's election.

The idea is "instant runoff voting," a vote-by-number system that is particularly well suited to multicandidate elections. It gives voters the option of expressing a second choice in a field of three or more candidates. If a voter's first-choice candidate comes in third or lower, that voter's second choice is counted. The sorting of ballots by second choices continues until one candidate has achieved a 50 percent-plus-one vote majority.

To illustrate, consider last week's election for governor. Republican Tim Pawlenty won with 44.4 percent of the vote in a race that included four major-party and three-minor party candidates. In an instant runoff system, that total would not have been sufficient for victory. But it's likely that when the second choices of people who voted for the five candidates who finished in third place or below were tallied, Pawlenty still would have achieved a majority of more than 50 percent.

In other elections, the presidential election of 2000 for example, instant runoff voting would allow people who favor someone like Ralph Nader to vote their conscience without fearing they might be helping elect the candidate who least reflects their views.

If instant runoff voting would have produced the same result in this year's governor's race, why try it? Here's why: Candidates must appeal to a majority of voters to win. A plurality isn't good enough. Speaking to and for only a narrow base of voters won't cut it.

Candidates in two-way races have always known as much. That knowledge is behind the politicians' two-step that is so familiar to American voters -- move toward one's ideological base to be nominated, move away from it to be elected. That's not a cynical dance; it's a necessary and important one. The majority-wins requirement of two- party politics has served this country well, producing governments of pragmatism and moderation.

When two parties give way to three or more, as has happened in Minnesota, a majority vote is no longer needed to win. Neither is majority appeal. The assent of a little more than one-third of those voting was sufficient to elect the current governor. It's not hard to imagine a future election that might be won with the votes of an even smaller slice of the electorate.

The better way to guarantee majority rule, some will say, is to discourage third parties. Make it more difficult for them to receive public campaign funds. Make filing for office more onerous. Further, some will predict that, after last week's poor showing, the Independence and Green parties will fade away before the next general election.

We doubt that Minnesota's third parties can be so easily discouraged. This state's tradition of political ferment is too well established, and voters' desire for wider choice too evident, for those whose ideas lie outside the two-party mainstream to fall silent. The inspiration they can draw from Independence Gov. Jesse Ventura's 1998 victory will long outlast his tenure as governor.

Rather than trying to stifle third parties, the Legislature would do well to adjust state election law so that multiparty politics can be practiced without sacrificing the benefits of majority rule. Instant runoff voting would nicely serve that goal.