Michigan, led by a liberal Democratic governor who fervently champions the cause of business, is emerging with surprising speed from the intensive-care ward of the nation's economically depressed "Rust Belt."

Unemployment has dropped from 17 percent two years ago to 10 percent today, state officials and businessmen rush from one ground-breaking ceremony to another, and words of confidence about the state's future can be heard everywhere.

Politicians and other leaders confidently assert that Michigan has an excellent chance of winning the extraordinary national competition that erupted months ago to become the site of General Motors' new Saturn small-car division.

If the state does not succeed, businessmen and politicians of both parties said in recent interviews, Michigan will do more than survive -- it will thrive.

Even Detroit, long one of the nation's most troubled cities, is experiencing a downtown building boom that has lifted its spirits higher than anything since its Tigers won baseball's World Series last year.

Much of the credit for this turnaround is given to, and claimed by, Gov. James J. Blanchard, a former four-term Democratic member of Congress who became governor in 1983. A major House sponsor of legislation that provided a financial bailout of Chrysler Corp., he does not mince words about his probusiness views.

" GM Chairman Roger Smith, Chrysler Chairman Lee Iacocca, Don Peterson of Ford, I'll name 'em all. They're all good friends. I work with them. I work with the head of the unions as well. I've seen what I think are the benefits of cooperation," Blanchard said.

One of the clouds forming on the horizon appears to be an unexpected move by Blanchard's GM friends to seek substantial property-tax reductions for facilities valued at $2.5 billion by local assessors in 20 townships and counties. Consumer activist Ralph Nader has called the campaign, which includes facilities in Ohio and New York, "avaricious."

A Nader organizer, James Musselman, has been touring the state, trying to organize opposition to the auto maker's efforts.

"We're watching it carefully, providing technical assistance to local communities. Different companies do this from time to time, but we're not about to launch a policy in which people don't pay their fair share of services," Blanchard said.

"I'm dealing with real problems, not with ideology. I've read all the books on industrial policy. And we've gone way beyond what's written and talked about. The people who write about these problems haven't dealt with a specific situation, to make it work."

But Musselman, from Nader's Washington-based Center for the Study of Responsive Law, said GM "wants to take very large amounts of money out of these small communities." Because many localities are seeking a piece of the Saturn project, he said, "GM has them over a barrel, but they're unwilling to say it because of Saturn."

The auto company has said the intensity of international competition has forced its vigorous review of such costs as local property taxes. GM, the world's largest auto maker, paid $222 million in combined Michigan taxes in 1983.

Blanchard acknowledged that "there's a little bit of truth" in the idea that the Saturn project has forced suitor states into a bidding war against each other.

But the governor, whose approval rating has climbed from a rock-bottom 30 percent two years ago to more than 60 percent now, rejects any suggestion that GM's clout gives it power to impose economic conditions solely to its liking, a "colonization" of Michigan.

"That's the armchair Georgetown view," he said tartly, "attention-focus on the big projects, such as Saturn or Mazda." Mazda broke ground last month for a $450 million auto assembly plant in Flat Rock, Mich., southwest of Detroit.

"But I go to ground-breakings for 50 jobs, like American Bumper & Manufacturing Co., in Ionia. We've cut taxes for small business, but we haven't cut taxes for big business in Michigan. That's not to say I wouldn't like to, but our priority is small business," Blanchard said.

"People who benefit from our regulatory reregulation are small companies who don't have a battery of lawyers and accountants and government relations specialists. It's not big firms," he said.

But Democratic State Rep. Lewis Dodak, the House majority leader, who estimates that 30 percent of his constituents work for GM, said the auto giant "is in a position that they can really put pressure on any state to change and offer a better deal."

"It's going to be a feather in anybody's cap if we can land it," he said. "But if not, it's not going to destroy the state."

The quest for Saturn has also done nothing to reduce friction in the legislature over proposed changes in workmen's compensation laws. Revision of them began four years ago, and the legislature is considering a new package of alterations aimed at further streamlining the claims and appeals process. Michigan has a backlog of 7,000 such cases, among the highest in any state.

Blanchard has pledged to continue the revision process. "But that's only one of many elements people evaluate for business cost. But we consider it one of the more thorny issues for us. We're trying to streamline that bureaucracy so there's one trial, not two; so we limit attorney's fees, and it stops becoming ADC welfare payments to lawyers."

State Rep. Doug Cruce of the Michigan House Labor Committee said, "We have to make significant reforms in workmen's compensation because of the extremely high cost it represents to business in Michigan."

State Commerce Director Douglas Ross added, "The environment is critical. We're attempting to define a new politics and a new public policy."