Barack Obama is reshaping American politics in more ways than we realize. There’s an interesting example brewing in Connecticut. Obama won the Connecticut primary on February 5, by a narrow margin, 179,349 votes to Clinton’s 164,831. The voting pattern was a lot like the 2006 Lamont-Lieberman primary result, with Obama as Lamont, winning the New York suburbs and the areas around the major universities, and Clinton taking the working-class suburbs of New Haven and Hartford, and most of eastern Connecticut. Unfortunately for her, as with Lieberman in 2006, this wasn’t quite enough.

That comparison implies that Clinton is stronger in Connecticut than her results suggest: again unfortunately for her, if she can’t beat Obama now, she’s not going to get another crack at it in November. But there’s another way of looking at February’s result, one that suggests that Obama actually underperformed. One of the ways that the Democratic Party tries to control who wins its nomination is through the superdelegate system. Another way, one it has in common with the Republicans, is by deciding who gets to vote in the primaries. Like a lot of states, Connecticut has a closed primary: only registered voters affiliated with a particular party can vote in that party’s primary. Requiring registration or, especially, affiliation well in advance of the vote is a way to deter insurgency candidates and to protect the interests of the party establishment.

This system worked against Obama. Democratic turnout was high, at 59 percent, but the unaffiliated voters who comprise 43 percent of the Connecticut electorate were, legally, not allowed to participate, which was the subject of confusion in the days before the primary, and the cause of some criticism after it was over. Given that most polls show unaffiliated voters prefer Obama to Clinton, the system almost certainly reduced his margin of victory. Not surprisingly, the leaders of the state’s Democratic and Republican parties have both defended the closed primary system. But Secretary of the State Susan Bysiewicz has called for a bill, similar to one that failed in the Connecticut General Assembly last year, allowing Election Day voter registration and affiliation. Bysiewicz, a delegate to the Democratic Convention, last week endorsed Obama: changing to a system of same-day registration would make it easier for future Obamas to ride to victory on a wave of late-hour enthusiasm from new and recently-unaffiliated voters.

It’s hard to know if it’s a good thing to give uncommitted voters this kind of power in a primary. Perhaps a party named the Democrats should not be too picky about who votes in their primary, no matter what it does to the party establishment, or the party’s chances of winning in November. But parties, and their establishments, exist for good reasons in the United States: they were not part of the vision of the Founding Fathers, but they rapidly became indispensable. It would be a curious irony if Obama’s sweep to victory as the new hope of the Democrats inspired changes in voter eligibility rules that were intended to make it easier to vote in primaries, but which had the long-run effect of contributing to the further weakening of Democratic, and Republican, party affiliation as a force in American politics.