One of the hazards of being mayor for 16 years is that the opposition can start using shorthand to run against you.

"Finnegan or him again," proclaims the campaign slogan of one of Boston's eight mayoral candidates, with no translation needed for a generation of voters to whom City Hall is a soap opera staring Kevin Hagan White.

Catchy as it is, the slogan may be premature. Then again, it may not.

After a year-long tease, White's public will learn tonight whether the embattled mayor plans to seek a fifth term. He's handled the announcement with lots of hush-hush and flourishes, booking five minutes of commercial time on the evening news of all three local stations at a cost of $25,000.

The betting in City Hall goes both ways. And there have even been reports, apparently unfounded, that the mayor prepared two speeches to foil anyone who tries to beat him to his announcement.

Meanwhile, the "Eight Pygmies," as White loyalists characterize the eager band of would-bes, have been having a hard time competing with Hizzoner High Tease for the attention of the public.

"He's managed to keep the race pretty much frozen," says former city council member Lawrence DiCara, one of the eight. "Kevin's not having made up his mind gives a lot of money people an excuse not to be with you."

"Is 16 years enough?" White asked on a radio talk show recently, adding not very helpfully, "That's the question on the public mind, and on my mind, too."

The local polls have already come up with an answer: By all means, yes! Pollster Patrick Caddell this spring found that among Bostonians White had a disastrous 31 percent favorable rating compared with a 66 percent unfavorable rating. And that 79 percent of the electorate agreed with the proposition that it's time for new leadership in City Hall.

But after every poll and every pol in town gets through burying White, not one has counted him out.

Much of the reluctance springs from the shape and timing of the mayoral race, a crowded primary at the end of September, followed six weeks later by a runoff general election between the two top finishers.

According to one popular scenario, White could survive the first round with barely a quarter of the vote, then find himself in a runoff with another finalist who appeals only to a narrow segment of Boston's richly varied electorate.

The common complaint against White is that he has grown bored with his job and that in his boredom he has grown sloppy, looking the other way while members of his administration have comported themselves in a way that has yielded seven indictments of high-level City Hall officials, six convictions and an ongoing federal probe of municipal corruption in the past three years. White pleads not guilty.

"Horowitz has been playing the piano since he's five years old on the same 88 keys," White said on the talk show. "People say to him. 'Well aren't you getting bored with those black and white things? There are only so many of them.' But there are nuances, and if you live with it, you stay with it."

While some believe the corruption probe will send White into political retirement, others argue that it will spur him into another race. White is a proud man, his intimates agree, and he doesn't want to appear to have been hounded out of office.

Others insist that whatever White's announcement tonight, decisions in 1981 and 1982 to lay off police and fireman during the city's bout with insolvency were his political undoing.

"That was Kevin White's Waterloo," says David Finnegan, a former school board president who gave up a lucrative slot as a radio talk show host to go after White's job. "People felt he was playing politics with public safety."

The prevailing view is that Finnegan, who has a glib and boyish charm, is the strongest of the crop of challengers. Other major candidates are DiCara, former state representative Mel King, populist City Council member Raymond Flynn, Sheriff Dennis Kearny and former transit administrator Robert Kiley.

However, Finnegan ran for mayor in 1979 and finished fourth, which makes some wonder if he desires the mayorship enough to withstand the demands of another campaign.