The vote that decided the DFL nomination for governor was closer than expected or than any candidate desired. But by Wednesday morning, it was clear that former U.S. Sen. Mark Dayton, not party and Star Tribune Editorial Board endorsee Margaret Anderson Kelliher, would advance to the Nov. 2 general election.

And by Wednesday afternoon, it was evident that nominee Dayton has a number of challenges on his hands. One is to defend his record against sharp partisan attacks. The state Republican Party quickly unveiled a TV ad that criticizes as "erratic" his U.S. Senate service, calling him "too risky for Minnesota."

In addition, Dayton must rally the DFL electoral base. Nearly three of five DFL primary voters preferred another candidate.

Dayton made quick strides toward meeting the party unity challenge, with considerable assists from gracious losers Kelliher and third-place finisher Matt Entenza. As they vowed they would, they joined him with hugs and handshakes at a unity rally at the Capitol and asked their supporters to back him now.

How willing DFL voters will be to heed their call will matter considerably as Dayton moves into a more hotly contested three-way race than the one he won Tuesday. The comparatively easy primary victories of Republican Tom Emmer and the Independence Party's Tom Horner give them more solid bases of party support as they vie for converts.

Dayton has several things in his favor. He won't be vexed by a party as emotionally divided as it was 30 years ago over abortion, guns and motorboats in the BWCA. Neither are DFL feelings bruised by a negative primary campaign. Instead, some morning-after analyses questioned whether the three DFLers had done themselves or their party any favor by refraining from publicly pointing out each other's flaws.

But Dayton has staked out a position on balancing the state budget that sets him apart from the rivals he defeated Tuesday and from a share of the independent voters any candidate needs to win a general election. Dayton would rely largely on an income tax increase for the top 10 percent of the state's earners to balance the state budget. Winning independent voters who have qualms about that approach to budget-balancing will require from Dayton a sales job worthy of the marketing skills of a memorable local department store that bore his family's name.

Dayton is also obliged to woo a party apparatus that he has spurned, not once but three times, in bids for statewide office. Despite the praise for the party's efforts to elect Kelliher that he voiced yesterday, his win deals a major blow to the caucus-to-convention process that endorsed her.

The party's full-tilt backing of Kelliher did not outweigh Dayton's advantages -- more money; greater familiarity among DFL voters, and a clearer, more progressive message. The DFL Party chose not to do for Kelliher what the GOP did for its nominee on Wednesday -- use its own funds to go on the attack on its candidate's behalf.

Tuesday wasn't the first time the DFL has suffered humiliation at the hands of one of its own partisans -- far from it. It's notable that the last DFL governor, Rudy Perpich, won the office in 1982 via the same insurgent's path that Dayton is following this year. DFL-endorsed candidates for governor or senator also lost primaries in 1966, 1978, 1998 and 2000. Each such defeat has generated talk of reform of the candidate selection process, but little action.

This time should be different. This time, DFLers should more critically rethink a selection process that has not produced a nonincumbent gubernatorial winner since 1970. Demographic changes in Minnesota and new technology join a dismal recent track record in auguring for a more open and broadly participatory way to choose candidates for major offices than the insider-dominated endorsement regimen allows.