Democrats Aim for Control in '84: Sen. Lloyd Bentsen (D-Tex.), chairman of the Democratic Senatorial Campaign Committee, said yesterday that he believed it was "do-able" for his party to win the five seats it needs to recapture control of the Senate in 1984.

The three states where the party's prospects appear brightest, he said, are North Carolina, where Gov. James B. Hunt (D) is expected to take on Sen. Jesse Helms (R); Iowa, where Rep. Tom Harkin (D) is expected to challenge Sen. Roger W. Jepsen (R), and Tennessee, where Rep. Albert Gore Jr. (D) is expected to seek the open seat created by the retirement of Sen. Howard H. Baker Jr. (R).

Bentsen also said that his fellow Texan, Sen. John G. Tower (R), will have a "tough time." Committee staffers later added the names of Sens. Gordon J. Humphrey of New Hampshire, Rudy Boschwitz of Minnesota and Pete V. Domenici of New Mexico as potentially vulnerable GOP incumbents.

Republicans, who took control of the Senate in 1980 and have a 54-to-46 majority, will be defending 19 Senate seats next year; Democrats 14.

"Of our 13 incumbents who'll be running, I don't know of any who is in trouble," Bentsen told a breakfast meeting with reporters.

Sen. Jennings Randolph of West Virginia is retiring, but "We have a candidate there and I don't think we'll have much trouble financing him," Bentsen said, referring to Gov. John D. Rockefeller IV.

He said the only serious potential challenge to a Democrat would come in Delaware if Gov. Pierre S. (Pete) du Pont IV (R) runs against Sen. Joseph R. Biden Jr. (D). "But I don't think he will try," Bentsen said.

He reported that his committee has raised $1.35 million in the first five months of this year, an increase of more than 50 percent over the comparable period in 1981.

"But $1.35 million is what our Republican counterparts raise in a lousy week," Floyd Fithian, the committee's deputy director and chief of fund-raising, said in a telephone interview.

In 1981-82, the National Republican Senatorial Committee outraised its Democratic counterpart by nearly 9 to 1. Fithian, a former Indiana congressman who unsuccessfully tried to unseat Sen. Richard G. Lugar last year, said he expected the huge financial disparity to persist.

Both Bentsen and Fithian predicted that Democrats will have more success this year in raising money from business, especially small businesses whose ranks have been thinned by record bankruptcies.