MACKINAC ISLAND, MICH., JULY 29 -- In the ambiance of this manicured island resort, 19 Democratic governors met with their party's eight presidential hopefuls today to gush praise and pledge support for the 1988 general election effort.

Their three-hour closed-door meeting this morning at the Grand Hotel was followed by a news conference in which the only trace of competition was over which governor's review of the party's presidential gladiators would be the most laudatory.

"This is the best field ever assembled by the Democrats," effused New York Gov. Mario M. Cuomo, who arrived late, departed early, but compensated by all but cornering the market on encomiums. "The only reason not everyone says that as a chorus is that not everyone knows them yet . . . . We have an embarrassment of riches . . . . Every one of them individually is better than the best the Republicans can produce."

"We have an all-American, all-star team," chimed in Democratic National Committee Chairman Paul G. Kirk Jr., and a half-dozen other governors added loud seconds.

The comity of the session -- in a party famous for internecine warfare -- was in its own way a testament to how unknown the Democratic field is and how shapeless their nomination contest remains.

Nobody here could be against anybody because barely anyone is for anybody. The Democratic governors' indecision reflects the attitude of Democrats at large, as reflected in many polls. The latest Gallup Poll of Democrats or those learning Democratic, taken July 10-13, found that 44 percent are undecided on their choice, a 6-point increase. That is the largest percentage of undecided voters recorded by Gallup at this point in a campaign since the 1940s.

Of the 26 governors who are members of the Democratic Governors Association, only two have picked a presidential favorite -- Tennessee's Ned R. McWherter, who is supporting his state's junior senator, Albert Gore Jr., and Vermont Gov. Madeleine M. Kunin, who is backing her neighbor, Massachusetts Gov. Michael S. Dukakis.

Dukakis, a fixture at governors' meetings during his nine years in office, said he expects eventually to have "substantial" support among his gubernatorial colleagues, but he made a point of not pressing for commitment during this gathering. "If I were in their position, I wouldn't endorse yet either," he said. "They need time to get to know us all."

Michigan Gov. James J. Blanchard, head of the Democratic governors' group and host of the retreat, said there is "probably some truth" to the proposition that many governors are predisposed to Dukakis, who is admired by counterparts for his competence and experience.

Even so, this field contains no one who is even a distant equivalent of Walter F. Mondale, an institutional warhorse who spent the year before the 1984 primaries and caucuses nailing down one endorsement after another. Moreover, unlike the Republican governors, who increasingly have come to view the GOP nomination fight as a two-man affair between Vice President Bush and Sen. Robert J. Dole (Kan.), the Democratic governors are frankly at a loss about how to handicap a race in which only one or two candidates consistently score in the double digits in national polls.

"At this point, it's a beauty pageant and I haven't picked a candidate," said Idaho Gov. Cecil D. Andrus. "I have the luxury of being able to look and listen and learn without being compelled to make a choice," said Virginia Gov. Gerald L. Baliles.

If there was a message the governors tried to convey to the candidates, it is that pragmatic rather than ideological politics will carry the day in 1988. "The Donkeys can be winners in 1988, but not riding the Great Society," Andrus said.

At least one Donkey -- former Arizona governor Bruce Babbitt -- is going to try to ride to the White House on a risky platform of tax increases, and his proposal for a national sales tax drew a tepid reception from party leaders here. Babbitt's plan would raise about $40 billion annually for deficit reduction; would include exemptions for food, clothing and other necessities; and would have other features to counter the regressive nature of such taxes.

His rivals for the nomination said they either opposed the idea or needed to hear more about it; several party leaders took issue with the political wisdom of calling for any kind of tax increase so early in the campaign. "The Democratic Party shouldn't be running on a platform of taxes," said Kirk.

"I reject the notion that we should have to come up with a plan to clean up the most outrageous deficit mess created by a man who talked piously of balanced budgets for 25 years," said Ohio Gov. Richard F. Celeste. Celeste has conducted presidential exploratory missions in recent weeks, but he did not ask to be treated as a candidate at this event. He said he will make a decision by September.

September is also the target month for a decision from Rep. Patricia Schroeder (D-Colo.), but she left little doubt about the way she's leaning. "I'm almost superstitious," she said of the enthusiastic response she has drawn on the stump over the past two months. "It's been so exciting; it's been hard to stay ahead of the brush fire."

Kirk held a breakfast with all the campaign managers to preach the love-thy-neighbor gospel, and at one point, he huddled with Dukakis' Paul Tully and Missouri Rep. Richard A. Gephardt's campaign manager, Bill Carrick. Dukakis and Gephardt are scheduled to debate one another in August, and some of the other Democrats have been less than pleased about being excluded. Kirk, Tully and Carrick all served at some point as political director to Sen. Edward M. Kennedy (D-Mass.), who did not exactly heed the call for intraparty unity when he chose in 1979 to run for president against an incumbent Democrat.

"We might as well enjoy the good will now," said one campaign manager, "because it won't last."