Boston voters will pick a mayor tomorrow and the names on the ballot will look very familiar. Incumbent Kevin H. White is seeking a fourth term and State Senator Joseph F. Timilty is trying for the third time to unseat him. Timilty nearly beat White in the 1975 election following the height of the Boston busing crisis, Watergate, and a series of attacks on the ethics of the White administration. The outcome of tomorrow's contest hinges on Timilty as the alternative candidate and on the changing nature of the city's population.

Kevin White admits that after 12 years the voters are looking for an alternative. But he has staked his campaign on the belief that Joe Timilty is not the man they're looking for. In fact, over the last eight years, none of the alternatives--Louise Day Hicks, David Finnegan, Mel King or Timilty--has drawn enough balanced support to unseat the mayor.

White created a strong coalition between heavy support from Italians, blacks, liberals and a strong minority vote from the city's Irish sections--South Boston, Dorchester, West Roxbury and Hyde Park. Timilty traditionally wins in the high-turnout Irish areas. He has never won by much; and the vote seems to be more anti-White than pro-Timilty. But the state senator lost nearly half his 1975 support there to School Committee President David Finnegan. Timilty needs these votes back in his column to have a chance tomorrow. Timilty must also pick up some black and liberal votes to counter White's rising popularity with the Irish. Yet he has done little to win liberal voter's support, evidenced by the ambivalent semi-endorsement "I won't be for Kevin" statements of State Representative Mel King.

In several of the light-voting student precincts near Boston University and Northeastern, WBCN disc jockey Duane I. Glassock, running a write-in campaign as a joke to promote his radio show, may challenge the state senator for second place.

Joe Timilty is not everyone's alternative to Kevin White. Safe money says not enough voters think he is their alternative. Even with the low turnout of a preliminary, White earned more votes in South Boston this September than he has ever earned there in a final election. He took Hyde Park this fall with the same number of votes that resulted in his losing the ward to Timilty in 1975. The mayor continues to have nearly unanimous support in the black and liberal wards and solid backing in Italian East Boston.

While it looks as if Joe Timilty is not the alternative this time, will the city in the future seek any alternative at all? The nature of Boston and its voters is changing. Since White has been mayor, and particularly over the past four years, the city's self-esteem has skyrocketed. Boston has become a model for urban living--ophisticated, chic, expensive and drawing new residents faster than the Larry Bird Celtics are drawing new fans.

By the 1983 election, gentrification will have expanded from Back Bay, the Fenway and the South End to the original streetcar suburbs--Charlestown, Brighton, Ashmont Hill and Jamaica Plain. More and more rising young professionals, children of affluence, born in VA-and FHA-financed suburbs, are opting for the brick townhouses instead of housing tracts and the Southeast Expressway traffic, and re-shaping the city with their Cuisinart, Volvo and exposed brick style.

Renovations for the waterfront area of Eastie, Southie and and Charlestown that White announced two weeks ago herald the changed atmosphere more affluent residents will bring. The theater district is becoming an established stop for shows on their way to Broadway. Quincy Market has more visitors than Disney World, and the Washington Street mall is earning downtown merchants record profits. Not to mention the Red Sox record-breaking ticket sales last year. People want to enjoy what a city has to offer. With a concentration of fresh enthusiasm and money, Boston's cultural life will explode, with even greater impact than it has in the last four years. To many of these residents, the city is providing the services and excitement they are looking for. And Kevin White is indirectly responsible.

Middle class citizens as well are potential White supporters, as long as a stable municipal government continues to meet their needs. Those conservative voters, predominantly making their homes in the southwestern section of Boston, have neither the liberal's luxury of worrying about the erudite issues, nor the poor's immediate demands for assistance. They pay close attention to police protection, school quality and property values--and these have returned to normal during White's tenure.

White entered the campaign for the final election with a tremendous lead. But the one thing that could hurt his chances almost did--a resurgence of racial tensions. Ironically, it is not with the black voters or the South Boston Irish that the city's racial problems have most hurt White's campaign. It is rather with the civic-minded middle class voters who just want the violence to end, the moderates who are the back-bone of White's coalition. Just as White began to deliver on his promise of stability, he seemed to lose control.

Although somewhat upstaged by the Pope's visit and the dedication of the Kennedy Library, the stonings of school buses in Southie in September and the shooting of Darryl Williams could have forced Boston voters to look at the alternative candidate a little more closely. But the recent violence, as the mayor asserts (and is having police commissioner Joseph Jordan prove), is more isolated than it was in 1974 and 1975. Local media polls indicate that White will still win the election.

Kevin White seems to have convinced citizens he can run a city in which both the new gentry and the middle class can live. The trend, however, is squeezing the poor. Both poor blacks and poor whites will find the pressures of living in an urban Beverly Farms--with higher property values and a more liberal social climate--too much to bear. Those that can afford to save enough will move to Quincy, Milton and the other inner suburbs; those who cannot will turn on the nearest and most vulnerable scapegoat--each other.

Both City Hall and satisfied residents will ignore the problems of these groups, though. The whites of West Roxbury and the liberals of the Back Bay will tire of the racial confusion and turn to chiding the poor for disrupting their comfortable city. Politically, the importance of the poor will dwindle as they make up a diminishing portion of the electorate. Blacks, students, tenants and poor whites simply don't vote in large enough numbers to make a difference. Socially they will be the outcast of both the affluent newcomers and the Irish establishment. The real challenge of the next White administration will be to protect the rights of the poor, avoiding the temptation to ignore them as a minor social and political nuisance.