A grinning John B. Anderson, presidential candidate, looked into the glass eyes of the network news cameras today and declared in his best TV anchorman voice: "And, my friends, that's the way it is, April 29."

It was a homemade joke, conceived on the plane down from Washington and delivered in a deadpan voice at the end of an Anderson stump speech.

He had, of course, borrowed the line from Walter Cronkite, America's favorite TV anchorman. He was, he said later, "exemplifying the politics of joy." And the crowd at Georgia State University loved it.

Cronkiet and Anderson were big news here today. Talk about the possibility of Cronkite accepting the vice presidency on an Anderson independent ticket was on the front pages of the Atlanta Constitution and the Atlanta Journal.

Cronkite, one of the most trusted names in the news, started it by telling Morton Kondracke, executive editor of New Republic magazine, that if Anderson asked him to be his running mate, "I'd be so honored to be asked, I wouldn't turn it down."

But it was one of those cute little political stories that went up the flagpole at dawn and was down by midday.

Cronkite, scheduled to retire next fall from CBS, issued a somber statement from an undisclosed retreat saying Kondracke has "misinterpreted our converstion."

"I have no interest in entering politics in any capacity," he said. "I have never endorsed a political candidate and I have no intention of endorsing a political candidate in the up coming campaign, including Mr. Anderson.

Kondracke, a respected political reporter, stood by his story, and Anderson took it with good humor.

Speaking tongue-in-cheek, he pointed to a bank of reporters at the Georgia State rally and said, "I can't think of any group of people who know as much about the problems of government" as people in the news media.

But he quickly added that he had never asked Cronkite or anyone else to be his running mate and that such talk was premature.

Later, Anderson conceded Cronkite's name may have come up within campaign inner circles. "People obviously in conversation will mention many things," he said at news conference. "His name surely could have been mentioned to me as a name that some day should be considered."

In Washington, campaign manager Mike MacLeod said he couldn't imagine where the Cronkite balloon came from. "We might get so far down that we'll have to offer the job to Dan Rather," he joked. Rather is scheduled to replace Cronkite as CBS anchorman next fall.

The incident pointed out the pitfalls of an independent candidacy. Anderson is sailing uncharted waters. Between now and November, he will have no primary elections to be judged by, no political convention to generate interest.

His biggest immediate task is to get on the ballot in as many states as possible. This has caused reordering of his campaign staff. A number of staff members have been fired from his former headquarters operation and he is in the process of hiring 10 young attorneys to work with Arnold & Porter, the Washington law firm he has retained, on ballot access problems.