MILWAUKEE--Mass. Gov. Michael S. Dukakis scored a convincing victory in the Wisconsin primary last night, cutting the Rev. Jesse Jackson's momentum in the Democratic presidential race and reaching for control in the struggle for the nomination.

"It was a great victory for us," Dukakis said, "I hope it's a sign of things to come," he added, looking ahead to the New York and Pennsylvania primaries later this month.

With returns in from 57 percent of Wisconsin's precincts, the Massachusetts governor had won 311,160 votes or 47 percent, Jackson had 197,795 votes or 30 percent, Gore 109,384 or 17 percent and Simon 31,389 or 5 percent.

Bush was winning 85 percent of the vote, to 7 percent each for Robertson and recent campaign dropout Sen. Robert Dole (R.-Kan.)

Dukakis also celebrated a narrow victory over Jackson in the Colorado caucuses, which were marked by a slow and controversial count. Together, Wisconsin and Colorado added to his slender lead in the competition for delegates to the Democratic National Convention.

For the Democrats, Wisconsin turned out to be a surprisingly important test in their nominating wars, a gauge of the struggling Dukakis campaign and of Jackson's surprising monentum. It was a prelude, as well, to delegate-rich primaries in New York, Pennsylvania and Ohio just ahead.

Dukakis worked hard in the state to quell party leaders' fears over his ability to fend off Jackson and attract blue-collar votes, particularly after the governor's poor showings in Illinois and Michigan last month. His victory seems likely to reassure establishment leaders, many of whom fear that Jackson would sink the party if he won the nomination.

For the same reason, the Dukakis victory is likely to stifle talk of drafting New York Gov. Mario Cuomo or another Democrat into the race.

Jackson aimed for a win in a state where only 4 percent of the voters were Black, in a bid for dramatic new stature in the contest.

The polls indicated that Jackson, who won the state's minuscule Black vote overwhelmingly, captured between 20 and 25 percent of the white vote as well. While this figure by far exceeded the 7 percent Jackson receivedin 1984, it was not enough to secure him amajority.

He said yesterday, "I feel good. After 40contests, I've come in number one or number two in30 of them. I'm proud of that."

The former civil rights leader campaigned hardhere, following his surprising Michigan caucusvictory late last month. He appeared on the coversof Time and Newsweek and drew large andenthusiastic crowds in a state where whites makeup more than 95 percent of the electorate.

But ABC poll analyst Doug Muzzio warned, "Wemay be looking at his ceiling here."

"We're seeing a dual electorate--a Blackelectorate and a white electorate," the analystadded. "Jackson does extremely well among Blacks,and Dukakis does substantially well among whites."

Despite the Dukakis victory, a CBS pollindicated that the governor's support was softerthan Jackson's or Gore's. It found that thegovernor's support was evenly split between firmbackers and those who liked him "withreservations," while Jackson's strong supportersby far outnumbered his weak ones.