''The least likely to succeed'' - that was the appraisal of Thirman L. Milner last spring when he decided to run for mayor of historic Hartford, capital and second largest city of Connecticut.
He did not graduate from high school; he has never held a city post, and he was first elected to public office only three years ago as a representative in the state Legislature.
But when Mr. Milner is sworn in as mayor today (Dec. 1), he will be the first black elected to head a major city in New England.
To be elected Mr. Milner had to challenge ''an institution'' (five-term incumbent Mayor George A. Athanson), demand a primary election recount, obtain a court compromise, win two primaries, and defeat two runoff finalists.
Mayor-elect Milner sees employment, job training, housing, and career development as keys to progress for both Hartford and Connecticut.
''Hartford is a city on the upswing,'' he says. ''Revitalization is the word. The corporate community is part of our revival.''
As mayor, he says, he will look to business and industry to reduce economic gaps caused by federal cuts, to the White House for benefits from the new federalism, and to the state government for block grants.
Hartford is ready for a black mayor, he says.
When he decided to run, Milner says, people told him the city already had too many blacks in key positions - fire chief, fire marshal, city manager.
''In my youth I remember there were no blacks in City Hall,'' he reflects. ''Two years ago when I was coordinator for Mayor Athanson's campaign, I had no idea I would be running against him this year. And the vote surprised me. Lots of good people from all over the city supported my campaign. And I won!''
Hartford is a city of many ethnic groups, but people are ''safe in any community,'' Milner says. He foresees no disrupting racial issues arising in the city.
His ''toughest job'' will be unifying City Hall, he notes. In a government in which the mayor and City Council have rarely pulled together, Mayor-elect Milner suggests two remedies - create a citywide mayor's advisory council, and plan a program to encourage more housing for the city.