Kate Michelman's decision not to run for Senate is a modern measure of our democratic health, not just in Pennsylvania, but nationwide. In a statement, she told us that "obligations to my mother, my husband, and my children preclude my being able to make this fight as a candidate."

If you believe that one, raise your hand.

Followers of politics in one of the key battlegrounds in the 2006 midterm elections suspect a different motive. Running as an independent would risk Michelman siphoning votes from Bob Casey and causing what to her and Democrats would be the worst-case scenario: the reelection of Republican Rick Santorum.

Michelman, a former president of NARAL Pro-Choice America, wasn't in it for herself. On the contrary, she planned to run to represent those people who felt unrepresented, maybe even betrayed, by the Democratic candidate. Now the danger is that a crucial voice may not find expression in the campaign, and abortion, an issue of great concern to many Pennsylvanians, could fall through the cracks.

But the problem is not peculiar to 2006. The word spoiler is a part of our national vocabulary. The idea that one candidate could ruin it for the closest ideological competitor has gripped the country since Ross Perot hurt George H.W. Bush in 1992 and Ralph Nader hurt Al Gore in 2000. Nationally, it happens frequently, among all parties, candidates of all leanings, and, as Pennsylvania just confirmed, independents as well.

When democracy can't accommodate more than two choices, we have a problem. Even if the prospect of spoiling doesn't deter candidates from entering a race, the anxiety is transferred to the voters. Should they vote for the candidate they favor, even if they think that candidate will almost certainly lose? There's no right answer when the majority can split its vote and elect neither of its preferred candidates. And, of course, candidates winning with less than a majority of the vote is a problem in itself.

None of this would have been an issue if instant runoff voting (IRV) were Pennsylvania's voting method. With IRV, instead of marking an "X" next to one candidate, voters rank them in order of choice. The counting uses voter rankings to simulate a series of runoff elections to determine a winner with a majority of the vote. That means that if voters' first choice were eliminated in the first round, their second choices would still count. No spoilers.

Burlington, Vt., made national headlines recently by using IRV in its mayoral election. The new system met with overwhelming popularity, and the electorate understood it well; 99.9 percent of voters cast valid ballots. The press eyed the race closely because of the potential for reform statewide, and the election was labeled "flawless." If mayors can be elected successfully with IRV, surely senators can.

People who care about their concerns being on the table need to think about the way our democracy accommodates them. Getting rid of the spoiler effect and embracing a majority voting system like IRV should appeal to people all across the political spectrum because there will always be times when they feel their concerns are not going to be addressed by two candidates. As a country, we can't afford to shut out independent voices.

This holds true whether that voice is Kate Michelman looking to fill a perceived hole in the Democratic party's priorities, or Tom Tancredo of Colorado, who could conceivably harass Republican presidential candidates from the right if he feels immigration is mishandled as an issue in 2008. Former Federal Reserve chairman Alan Greenspan recently decried the "polarization" of American politics, saying the time was ripe for a more centrist third party presidential candidate.

Michelman's decision not to seek a Senate seat reflects more than the political dynamics of the day - it spotlights a grave democratic problem. Fortunately, there is a commonsense solution.