AUGUSTA — Angus King officially became the nation’s lone independent governor Wednesday in a clear rejection of partisan politics and “business as usual” in state government.

Late Wednesday afternoon, with 97 percent of Maine’s 664 precincts reporting, King received 35.8 percent of the vote, followed by Democratic nominee Joseph E. Brennan, with 34.3 percent. Republican candidate Susan M. Collins finished third with 23.3 percent and independent Green Party candidate Jonathan Carter earned 6.6 percent of the vote.

The 50-year-old Brunswick lawyer promised to end the partisan squabbles that have come to epitomize State House politics in recent years and get Maine’s economy back on track. A former public television talk-show host, King ran an energy conservation company that he recently sold for $20 million.

A registered Democrat until last year, King left the party and became the state’s second independent governor since the 1974 election of James B. Longley. His first attempt at elected office was achieved largely at his own expense, after pumping $1 million into his $1.6 million campaign.

Relying on a “just plain folks” approach that belies his Dartmouth educational background, King published a book about his vision for Maine that was lean on specific remedies to improve the state’s faltering economic condition. His plan to replace a business tax on machinery and equipment with a higher corporate income tax was one of the few specific recommendations made in a campaign in which most of the candidates were short on details. Ironically, it was the one that plagued him the most when his opponents attacked the plan as an attempt to raise taxes by $100 million.

Facing a considerable challenge in Brennan, a former two-term governor, King was able to make significant inroads in Brennan’s Democratic base, nailing him in traditional party strongholds such as Saco and Lewiston.

In addition to his raid on Democratic votes, King was warmly welcomed by a prominent and well-heeled segment of the Republican party who turned their backs on the GOP nominee. Dennis Bailey, King’s press spokesman, estimated that Republican support exceeded 50 percent in some southern Maine communities.

Brennan’s unsuccessful showing in the election may have stemmed not only from his inability to attract new voters, but also his failure to retain the traditional base of support on which he has been able to rely in many previous political outings. At 60, the oldest of all four candidates, Brennan was forced to confront criticisms that his time had come and gone. The Brennan campaign also was viewed with some disdain by King’s supporters for pushing a number of negative ads that were later denounced as misleading and erroneous.

After winning an eight-way June primary, Collins was immediately attacked by ultraconservatives within her own party for her pro-choice views on abortion and support for a gay rights law in Maine. Although authorities said she was not involved, Collins suffered in the polls after her brother was arrested in a large marijuana bust this fall.

A former staffer for Sen. William Cohen, Collins of Standish was abandoned almost immediately by the Republican upper-crust residing in the southern Maine GOP enclave known as “the Gold Coast” that stretches from Falmouth to Freeport.

Robert A.G. Monks, a GOP campaign financier and former party state chairman, announced his support for King in the last week of the campaign when staffers with Sen.-elect Olympia J. Snowe and outgoing Gov. John R. McKernan privately denounced the Collins candidacy.

Carter’s 6.6 percent share of the vote met the 5 percent threshold needed by Maine Greens to establish the Green Party as an official party. A former university instructor, the Lexington Township activist ran two years ago for the 2nd Congressional District.