BOISE, Idaho (AP) _ Burdened by an outspoken ex-wife, a son facing criminal charges and a formidable political opponent, Steve Symms, a fixture in Idaho politics for two decades, is reportedly considering quitting the Senate.

The Idaho Republican who spent four terms in the House before beating Sen. Frank Church in 1980 has not said whether he will run for a third term next year. He has promised a decision by Labor Day.

Until then, ''He has nothing to say about it,'' Symms' spokesman, Bill Powers, said recently.

Meanwhile, Idaho Republicans are fearful of a mad scramble for Symms' seat, as Democrats try to add to their 56-44 edge in the U.S. Senate in 1992. One- third of the Senate's 100 seats will be up for grabs that year.

''The Democrats have targeted the state of Idaho to pick up the seat for their party,'' said Wendy Burnley of the National Republican Senatorial Committee. ''Holding onto the seat is of utmost importance to us.''

A Democrat who says he plans to seek the job is four-term Rep. Richard Stallings.

Stallings has had little to say about Symms' personal problems, but he has noted that the senator once supported limiting Senate service to 12 years.

Symms, 53, won't discuss recent suggestions by his ex-wife, Fran, that he was unfaithful or talk about his son Dan's indictment for allegedly breaking federal immigration laws at the family fruit ranch.

But he did say in a recent interview, ''No matter what people have been saying about me, I have never lost sight of my love for Idaho and my love for America. If I run, I am going to win that election.''

Both personal issues have been the subject of scathing editorials throughout Idaho. A headline above an editorial about Symms' treatment of his ex-wife said, ''First he duped her, then he dumped her.''

The senator is engaged to his former aide Loretta Fuller, who is now an executive assistant to the Senate's sergeant at arms.

But state Republican Party Chairman Phil Batt, a Symms ally, says more than personal problems is causing the senator to evaluate his political future.

''It's a genuine mid-life appraisal of whether you want to spend additional years in public service or try to do something else in life,'' Batt said. Before politics, Symms worked at the family fruit farm.

Symms was a friend of Sen. John Heinz, R-Pa., who was killed in an April plane crash. Heinz' death might have given him cause to think twice about running again, Batt said.

''Steve was already talking previous to that about maybe calling it good, but I think it was another factor,'' he said.

While Symms ponders and other potential GOP candidates stew, the senator is continuing to maintain a high profile on political issues, speaking out on crime, highways and rural medical care.

Noted for his outspokeness, he once said the problem with the Soviet Union's Chernobyl nuclear accident was that it wasn't closer to Moscow.

Another time, he lectured a delegation of Soviet women visiting Idaho on the failings of communism.

When former Massachusetts Gov. Michael Dukakis ran for president in 1988, he said he had heard rumors that Dukakis' wife, Kitty, once burned an American flag.

''I've never claimed to anybody that I am perfect,'' he said.