Governors' races: storm cloud on GOP horizon. Soundings reveal a significant Democratic edge; the 'new federalism' may be one loser

President Reagan may hold the White House, but his party is in danger of losing its grip on many of the nation's statehouses.

A Monitor survey of races in the 36 states whose top offices are being contested this fall gives the Democrats a 2-to-1 edge. This points to a considerable widening of their current 27 to 23 lead in governships.

Such an outcome, anticipated by strategists in both parties, would appear to reverse prospects for a sweeping Republican political takeover, as heralded by the 1980 elections. And it's taking shape at a time when the President is counting on the states to join him in a new division of federal power, his ''new federalism.''

''Sure it's significant,'' says Thomas E. Mann, executive director of the American Political Science Association, ''and not only because of the state of the economy. Given the fact that more Democrats are up than Republicans for the governorships, and that only a few months ago we were talking Republican resurgence, the Democrats' advantage is highly significant.''

The governors' races may eclipse the Senate and House races in drama and significance, observes Michael Barone, Democratic pollster and author of ''The Almanac of American Politics.''

''They're going to be debating some very basic questions - what governments are supposed to do, how far the welfare state should go,'' Mr. Barone says. ''They're faced (in the states) with getting their own economies moving. Next to these races, the congressional elections are rather predictable. The most intellectual substance may be in the governors races.''

For President Reagan, to push too hard now for his ''new federalism'' plan could give Democratic gubernatorial candidates too much of an issue. Pervasive Democratic governorship gains this fall might be read as a rejection of Reagan's new federalism, and strengthen the Democratic governors' bargaining power. Thus the President has kept a cordially open door to the counterproposals offered by the National Governors' Association meeting here this week.

At issue too are the political power bases up for grabs this fall. Of the 36 governors races in November, seven include the biggest states -- California, New York, Pennsylvania, Ohio, Michigan, Illinois, Texas -- with 44 percent of the nation's population. The Democrats are ahead in four of these -- the three Midwest states now held by Republicans, plus New York. California is rated a tossup. The Republicans have the edge in Pennsylvania and Texas -- but the Democrats are eager to do battle in the Lone Star State.

A survey of the 36 governors races, based on the political assessments of experts in both parties, shows the Republicans weakened most among the industrial crescent states, from New York across the Great Lakes into the Midwest heartland - where recession, unemployment, and other economic burdens have fallen heaviest.

In all, 20 governors seats now held by Democrats, and 16 by Republicans, will be decided in November. If the Democrats pick up four Republican seats, the current average estimate, they would take 24 seats to the Republicans' 12. By historical standards, such gains would be modest. The Republicans lost 10 seats in 1970, 9 in 1954, and 12 in 1922 in midterm governors races when GOP presidents were in power.

''I'll be happy if we break even,'' says Carol Whitney, executive director of the Republican Governors' Association. ''The general feeling, among people like (Democratic pollster) Peter Hart and (Republican pollster) Robert Teeter is that we may be only down three to six - which kind of surprises me, because traditionally when we hold the White House we lose 9 to 12.''

''I fully expect the Democrats to take at least several seats this year,'' says Michael Gage, executive director of the Democratic Governors' Conference. ''The state of the economy will lead to a strong Democratic resurgence in the Midwest, where so many Republican governors are retiring.''

Estimates of the edge in races this early in a campaign, with some candidates unannounced and primaries still to be waged, are at best descriptive. Assessments by experts in the two parties are closest in the East and Midwest, with the Republicans claiming to sight opportunities in a few Western and Southern states.

In the East, the Democrats are expected to keep their 3-to-1 edge. New York Mayor Edward Koch's entry into the New York race greatly enhances the Democrats' chances to retain the governorship in that state, Republicans say. In Pennsylvania, incumbent Republican Richard Thornburgh could be beaten if a strong Democratic candidate emerges to take him on, Democrats say.

In the Midwest, the Republicans' 7-to-1 edge in governorships is threatened. ''With Michigan's Milliken, Iowa's (Republican incumbent Robert D.) Ray out, all these little events are happening,'' says one Democratic strategist. ''The whole thing is a house of cards set up to fall for us this year.''

In the West, the Democrats hold seven seats to the Republicans' three. The big question mark is California. Los Angeles Mayor Tom Bradley is expected to win the Democratic nomination. But whether Bradley, a black, will be able to attract middle-class white votes outside Los Angeles is unclear.

The Texas race also looms large, with implications for the future of both President Reagan and the Republicans.

''I'll still give the Republicans an edge in Texas,'' says a Democratic strategist. ''But that one is going to be a fight. (Republican Texas Gov. William) Clements and Reagan have both lost ground among two groups of voters in Texas -- the Hispanics, and older white rural voters.