Blanche Lincoln’s victory over Bill Halter in last night’s runoff election was not a crushing defeat for the progressive movement, though it certainly hurts. It was more like a missed opportunity.

The progressive groups that endorsed Halter—from labor to environmentalists to netroots activists—accomplished a lot in a short period of time, building an incredible organization from scratch in three months on difficult terrain. Ultimately, it wasn’t enough. Knocking off an entrenched incumbent is very, very difficult—the craziness of 2010 has obscured the fact that, before this election cycle, only four incumbent senators had lost their primaries in the past two decades.

Arkansas was always going to be a tough place to pull off an upset of this magnitude. From the beginning of this race, there was a disconnect between the progressive movement’s aspirations and the realities of Arkansas politics. Halter’s natural coalition should’ve been Obama voters who were fed up with Lincoln’s defiance of the president, but there just aren’t that many of those types in Arkansas, and a lot of base Democrats stuck with Lincoln out of residual loyalty or because they just never got to like Halter, who ran a focused, disciplined campaign but was unable to shed the icy and overly ambitious image that surrounds him. In Pulaski County, for example, the home of Little Rock and the largest and most liberal county in the state, Lincoln beat Halter by seventeen points. In contrast, Obama beat McCain there by a dozen points in 2008, even though he lost Arkansas by twenty. During the first election in May, Halter did surprisingly well among conservative Democrats in rural southern Arkansas who showed for their local primaries and voted for him because they didn’t like Blanche. They didn’t show up a second time.

These facts have more to do with the peculiarities of local politics than with a broader failure by the progressive movement, which was rejuvenated and united by this race, even in defeat. Next time they have to organize in a red state like Arkansas, they’ll do better. Learning experiences are frustrating, but they are not worthless.

“Sometimes you can win by losing,” Tom Swan, Ned Lamont’s former campaign manager in Connecticut, told me a few months back. Incumbents usually don’t go down with the first blow; it takes a flurry of sustained punches before they fall. Despite the final outcome, the activist groups supporting Halter’s candidacy sent a message this spring to those Democrats who have most egregiously thwarted Obama’s agenda or repeatedly changed positions on big issues based on political convenience: watch your back. This is a good fight for Democrats to wage—and it won’t be over anytime soon.