Sen. Dale Bumpers (D-Ark.) has told his closest advisers that he has decided not to seek the 1984 Democratic presidential nomination, and he plans to announce his decision today, according to sources close to him.

For months, Bumpers had vacillated between running and not running as he traveled the country seeking advice and support, both political and financial.

He made stump speeches and appeared at party events in California, Georgia and Massachusetts alongside the six Democrats who are actively in the race.

Increasingly, those closest to him became convinced that Bumpers soon would officially join the ranks of the runners--and as late as Friday he still was talking privately as if he were a candidate. But Bumpers informed his political associates in telephone calls Sunday and yesterday that he had decided against making the race.

He gave no reason, according to one who spoke with him, but said he had come to the decision on Saturday.

"I think it just came down to the fact that ultimately he was not driven with enough desire to run," this adviser said. "I think he was convinced that it was do-able for him. He had some distance to come, but it was do-able."

Bumpers frequently had talked of the problem of raising enough money to make a credible run for the presidency--especially because he would be starting months later than the others. But this source added that he did not think that, in the end, Bumpers' decision was dictated solely by fiscal concerns.

"I don't think money was the overriding problem," this source said. "I think it was purely a personal decision."

At one point, this source added, Bumpers had asked: "Why in the world would you want to give up the best job in the world being a senator for the worst job in the world being president ?"

Bumpers scheduled a news conference in Little Rock at 2:30 p.m. today.

According to Ginger Yates, a secretary in his office there, "at that time he will make known his plans."

His decision perhaps boosts most significantly the prospects of Sen. John Glenn (D-Ohio), who because of his status as a former astronaut and his centrist views is counting on the South as a significant source of strength.

Glenn strategists did not relish the prospect of having Bumpers, a moderate southerner who is a strong orator and campaigner, join the battle for delegates in the South, along with Sen. Ernest F. Hollings (D-S.C.) and former governor Reubin Askew of Florida.

Bumpers' decision also should spell political relief, of sorts, for former vice president Walter F. Mondale and Sens. Gary Hart (D-Colo.) and Alan Cranston (D-Calif.) because Bumpers already had begun to interest a number of Democratic Party liberals. Among them were supporters of Sen. Edward M. Kennedy (D-Mass.) and Rep. Morris K. Udall (D-Ariz.), two prominent liberals who also decided not to run.

"It seems to me if one wants the job too badly, it may sustain one in the campaign, but that does not assume that a successful presidency will follow," Bumpers told The Washington Post late in February. "Because if you want it too badly, you are likely to compromise yourself."

Yesterday one political associate who had been informed of Bumpers' decision said:

"He could see the first $1 million, but he had no idea where the money would come from after that . . . the money he would need in September. I just don't think he ever reached the point where he wanted it enough to sacrifice his personal and family considerations. He is a very cautious decision-maker."