The nation's best-known muckraker, Jack Anderson, has spent the last week fending off the accusation, published in The Nation, that he has gone soft on Ronald Reagan.

The article, written by Washington correspondent David Corn, also charges Anderson, whose column appears in about 850 papers including The Washington Post, with having business dealings with people The Nation considers politically or economically unsavory.

"Unadulterated McCarthyism," fumed Anderson earlier this week. "Except that McCarthy indulged in guilt by association. Corn tries to link me with people I haven't even associated with."

Corn wrote that one of Anderson's business partners is Max Hugel, who resigned his position as chief of clandestine operations at the CIA in 1981 after business associates accused him of improper stock trading. Anderson said that Hugel is associated with a television production company that has contracted with the columnist to do documentaries and other programs.

"That's a little like me calling David Corn a business partner of Arthur Carter, who owns The Nation," Anderson said.

Anderson said the columns that Corn used to demonstrate how he has pulled in his claws for a president he apparently likes personally were written not by him but by his partner, Dale Van Atta, who has also been tough on the president.

Anderson added that the Nation article appeared the same day that an Anderson column accused Reagan himself of ordering the United States to violate the Anti-Ballistic Missile Treaty with the Soviet Union by proceeding with an aspect of the "Star Wars" program.

"Usually the right wing does it to me," Anderson said. "It's a little troubling to have a hatchet job done on me now by a magazine I basically respected. I suppose it's a good thing, though. If you're attacked from the left and the right, maybe that's where you belong."

Olympia Brewhaha

Brian Basset's cartoon about the Hanford nuclear facility last July had a lot of Seattle Times subscribers laughing. One of them wasn't the Pabst Brewing Co., which makes Olympia beer.

Olympia beer has a can with a horseshoe framing a waterfall. For years, the word "Tumwater" (the name of the town where Olympia is brewed) appeared; it was later replaced by the phrase "It's the Water."

Basset drew his beer can with a horseshoe on top and a barrel dripping toxic wastes. The name on the label was Hanford and the slogan was: "It's the water." The list of ingredients read, "cyanide, carbon tetrachloride, chromium, water and a whole bunch of chlorinated hydrocarbons."

Pabst lawyers are arguing that readers might not realize that Basset was talking about Hanford Nuclear Reservation and could think Olympia was really using such poisons, maybe as preservatives.

In a lawsuit asking for more than $1 million, the brewers also say that Basset infringed on their trademark.

The Seattle Times is responding that readers, even those who drink Olympia, would have no trouble figuring out that the cartoon was about Hanford. The newspaper also argues that cartoons are an expression of opinion and thus deserving of special protection under the First Amendment.

Calls to most of the main watering holes in Seattle found bartenders suggesting loftily that you could buy Olympia only in the grocery stores. A spokeswoman for Safeway, which has about 80 stores in the Seattle area, said she knew of "no complaints" about Olympia beer as a result of the Seattle Times cartoon.

The Graying of a News Service

The idea is terrific. People are getting older; older people read a lot. So why not have a special news service for the "adult" population, as the 50-plus age group is sometimes called in advertising copy.

The problem is that the Maturity News Service, which The New York Times Syndicate launched and started distributing recently, is "underwritten" by the American Association of Retired Persons, a group that lobbies in behalf of its 27 million members. The AARP provided the seed money to help start the news service and now pays the rent for offices in the National Press Building, according to Maturity News Service managing editor Robert Horton.

In recent years such cooperation has been considered unusual or even off limits by some of the ethicists in journalism. Ken Cummins, Washington correspondent for the Fort Lauderdale (Fla.) News and Sun-Sentinel, wrote in a column that "the venture seems more than just a bit strange because newspapers usually avoid getting in bed with advocacy groups such as the AARP out of concern that the relationship will raise questions about the objectivity of the paper's news coverage."

Cummins also noted that there had been a glowing article about the AARP in The New York Times, which catalogued the group's growing clout in Washington.

The managers of the Maturity News Service reportedly were furious. Clifton Daniel, former managing editor of The Times, sent a letter to Cummins' editor Eugene Cryer, complaining that it was a cheap shot.

"A ridiculous column it was," said Rob Roy Buckingham, who is consulting editor of the news service for elderly readers. "When we got into this thing we realized that if we were ever perceived as being a propaganda arm of the AARP, it would never work. We know that and the AARP knows it."

Speaking for himself and others with backgrounds in journalism involved in the news service, Buckingham said that "if it came unstuck, we would probably all resign."

Cryer said he passed Daniel's letter on to other editors, but thought Cummins' column was fair comment on an argument in the journalistic community.

"He's not in any trouble, that's for sure," Cryer added.