Robert Graham, multimillionaire, took his campaign for governor into the sewer the other day. He stayed eight hours, through the hottest part of the day.

The event was hardly a memorable one. Graham, 41, simply put in a day repairing a storm sewer with the Triple R Paving Co. Nobody would have noticed if the television crew hadn't come up from Miami, and a photographer from the Fort Lauderdale News hadn't dropped by.

But they did. And Graham's sweatladen brow appeared on the evening news and across four colums of the front page in the afternoon newspaper.

Graham's election gimmick - spending a day working at 100 different jobs - had scored again. He was understandably pleased.

"If we would have given a speech on economic development to the Fort Lauderdale Rotary Club and given the greatest speech ever delivered on the subject, do you think we'd have gotten this kind of coverage?" Graham asked later, slapping the front page of the newspaper. "You know it would have been on the back page, if it made the paper at all. Which would you rather have? This or that?"

Graham, a little-known state senator before the campaign, is one of six Democrats running for second place in today's Florida Democratic primary. Seldom have so many candidates spent so much time and money trying to be No. 2.

The reason: every poll conducted this year concedes the first spot to state Attorney General Robert Shevin. But in all probability he won't collect enough votes - 50 percent - to avoid a runoff Oct. 10.

Florida has a recent history of the second-place finishers in primaries winning runoffs. "Whoever comes in second will be the nominee," state Republican chairman Bill Taylor declares without reservation. "Shevin will get all he'd going to get the first time around."

The governor's race has a little something for everyone: big money, a father and son team with a well-known Florida name, the hint of scandal, a divisive battle over casino gambling, and a former Republican governor running as a Democrat.

According to a poll conducted last week by five of the state's major newspapers, Shevin is going into the election favored by 29 percent of the voters, Graham by 14 percent, Secretary of State Bruce Smathers, by 6 percent, Lt. Gov. James Williams by 7 percent, and former Republican Gov. Calude Kirk Jr. and Jacksonville Mayor Hans Tanzler, both by 6 percent. Thirty percent of those surveyed were undecided.

In the Republican primary, Rep. Lou Frey has charged that his opponent Jack Eckerd, a drugstore chain owner, should withdraw from the race because of alleged irregularities during the 15 months Eckerd directed the General Services Administration.

But, according to the poll, Eckerd, who has spent more than $1 million of his own money in the campaign, held a comfortable 57-to-22 percent lead over Frey, and appeared strong enough to avert a runoff.

Kirk, whose four years as governor during 1960s were marked by excess and confrontation, is the most interesting candidate in the Democratic race, providing comic relief if nothing else.

He has run a one-issue campaign on a shoestring, bombasting his opponents. Smathers, for example, he says, "is a 34-year-old little kid who can't talk unless his daddy writes a press release." He has nicknamed Eckerd "the Evil Ego."

His issue is legalized casino gambling.Every other candidate, Republican and Democrat, opposes it. But Kirk sees it as the salvation to what he calls "the dying, decaying, geriatrics ward" - Miami Beach.

A proposal to legalize casino gambling will appear on the Florida ballot in November.

For weeks, the Democrats' battle for second place has focused on Graham and Smathers.

Smathers opened the race well in the lead, relying largely on the name of his father, former U.S. Senator George Smathers. He vowed to make teachers take tests to weed out incompetents, and veto any new taxes pressed by the legislature. He charged Graham was trying to "buy" the election.

But his campaign appeared stalled in deadwater until recent weeks when his father was called on to raise money and campaign with his son.

The father and son team appeared Saturday before a group of Cuban-Americans in Miami's Little Havana section.

It was a sentimental journey back in time. There were many toasts and embraces. The younger Smathers speaks fluent Spanish; the senior Smathers is a hero among Cubans for the help he gave exiles after the Castro revolution. And almost everyone there had a personal story about him.

Like a coach will a new secret play, he rallied the troops, touching emotional heartstrings.

"There is a great tradition of family honor among Latins," said Smathers, slim, tanned and well tailored. "You understand how I feel about my son. You know how important this election is to me. My son has his reputation on the line.He has his future on the line. If someone would help your son, you'd be eternally grateful. If you help my son, I'll be eternally grateful to you."