In Minnesota, Democrat Rudy Perpich, a maverick dentist from the Iron Range, is so confident of winning the governorship that he has put a transition team to work.

In Ohio, where Democrats have controlled the governor's mansion in only four of the last 20 years, party chairman Paul Tipps talks about winning "the biggest Democratic victory in history."

In Michigan, where blue-collar workers gave Ronald Reagan a big boost in 1980, Rep. James J. Blanchard, the Democratic gubernatorial candidate, talks about leading "a big sweep" that will signal "a rebirth of the Democratic Party in the heartlands."

This looked like a big Democratic year in gubernatorial races in the hard-pressed Midwest because five incumbent Republican governors, four of them popular favorites for reelection, decided to retire.

If polls in these states are accurate, it could be a bigger Democratic year than anyone expected. Democratic gubernatorial candidates hold leads of 15 percentage points or more in recent polls in Ohio, Michigan, Minnesota and Wisconsin. In Iowa, a race once written off by Democrats has become surprisingly close.

Democrats, who hold 27 of the 50 governorships, are almost certain to gain at least five and possibly as many as 10 in the 36 governor's races to be decided next week. In addition to the five open statehouses in the upper Midwest, incumbent GOP governors are in perilously close races in Arkansas, Nebraska, Nevada, Oregon and Texas.

Almost everyone says margins indicated by polls will close during the final week of the campaign, however.

"I'm suspicious of our data. There's a certain political structure to all of these states," Republican pollster Robert Teeter says. "Historically nobody, Republican or Democrat, has ever won by these margins."

But in the Midwest, the Democrats have launched their fiercest offensive. Here Republicans lead only in Illinois, where Gov. James R. Thompson is easily beating back the challenge by former senator Adlai Stevenson III.

Plant closings, bankruptcies, high unemployment and low farm prices have made an economic disaster area of the region, which Reagan carried in 1980. State governments face record deficits and choices between tax increases and cutbacks in government services.

"Reagan's economic strategy cut hard against the heartland, and the heartland understands it," declares Richard Celeste, Democratic gubernatorial candidate in Ohio. "By and large, we've shouldered the worst of the recession."

Unemployment, 10.1 percent nationwide in September, has been a Republican albatross in the region. It stands at 12.5 percent in Ohio, 14.5 percent in Michigan, 10.4 percent in Illinois, 10.4 percent in Wisconsin, 8.3 percent in Iowa and 7.3 percent in Minnesota.

The region's gubernatorial races pose unusually sharp ideological differences.

Democrats, who have assiduously avoided the liberal label recently, are embracing it. GOP candidates, by inclination and necessity, have embraced Reagan's economic programs, often with eloquence and deep feeling but also with anxiety.

In state after state, jobs are the main issue and the argument is about which party can deliver them: