Closed primary is best.

Byline: The Register-Guard

Both major political parties in Oregon have now experimented with allowing independents and other unaffiliated voters to vote in their party primaries. And both parties decided to end the experiment, the Republicans in 1993 and the Democrats last week. The parties' decisions to return to the traditional closed primary were sound.

In a closed primary, only voters registered as members of that party may vote on partisan races in the primary election. All registered voters, including independents, can vote in the primary on nonpartisan races and measures. Under the open primary system, voters registered as independents could request a Democratic or Republican ballot and vote in that party's nominating contests. Oregon Republicans opened their primaries in the 1990 and 1992 primary elections, and the Democrats tried open primaries in 1998 and 2000,

The parties hoped that by allowing nonaffiliated voters to help choose their nominees for the November general election, they would enlist the support of the ever-expanding number of independents - who comprise a fifth of Oregon's registered voters today. The idea was that if an independent voted in, say, a Republican primary, he or she would be more likely to stick with the party in the fall. There was also the hope that an independent who became involved in nominating a party's candidates might be persuaded to register in that party.

The parties are right to be concerned about eroding membership, but the open primary had several drawbacks.

The biggest was that only a small percentage of independents bothered to ask for Republican ballots in 1990 and 1992 or Democratic ballots in 1998 and 2000. Participation by independents reached its highest level in 1990, when 11 percent of independents bothered to vote in the GOP primary. The percentage gradually kept falling until the 2000 primary, when fewer than 5 percent of the state's independents voted in the Democratic primary.

Another drawback is that independents are just that - independent. They don't belong to one of the major parties for a variety of reasons, the main one being that they want to pick and choose from among all candidates, and resist being drawn into close association with either major party. This makes independent voters the swing votes in close general election contests, meaning that candidates must take into consideration the causes and concerns of independents.

Still another flaw that an open primary invites is mischief-making and gamesmanship. It's possible - even if unlikely - for, say, a Republican candidate to persuade independents to vote for the weakest candidate in a hotly contested Democratic primary race to make it easier for the Republican nominee to win in the fall. There's no hard evidence that such things have occurred, but the possibility does exist.

A final downside to the open primary is that it inflates the cost of campaigning because candidates must appeal to a larger universe of voters.

The closed primary remains the preferred system because it restricts the nominating of partisan candidates to the members of a party. Those are the folks who should choose which candidates march under the party's banner in the fall election.