Undated (AP) _ A California television commentator and speech writer under Richard Nixon said he is seeking the former president's support in his bid for the U.S. Senate, while the grandson of Franklin Delano Roosevelt kicked off his campaign for Massachusetts' 8th Congressional District seat.

James Roosevelt Jr. faces another candidate with a famous name in the crowded Democratic primary - Joseph P. Kennedy II, 33, son of the late Sen. Robert F. Kennedy.

''I learned long ago that it is not the name that makes the man. It is the man behind the name that really counts,'' Roosevelt said Tuesday, quoting his grandmother Eleanor.

More than a dozen candidates are competing in the Sept. 16 primary to succeed retiring U.S. House Speaker Thomas P. O'Neill Jr.

A Harvard Law School graduate, Roosevelt now works as an attorney with a Boston.

A woman who resigned as a White House adviser a month ago began her U.S. Senate campaign today in Maryland in an uphill quest by the Republican Party to retain the seat of retiring Sen. Charles McC. Mathias.

Linda Chavez, 38, staff director of the U.S. Civil Rights Commission before she joined the Reagan White House, said she plans to concentrate her campaign on the issues of education, crime, poverty, national security, defense and the economy.

Ms. Chavez, who moved to Maryland in 1984, faces at least two opponents in the GOP primary in September. Maryland Democrats hold a 3-to-1 voter registration edge and those competing for that party's nomination include Gov. Harry Hughes, Rep. Barbara Mikulski and Rep. Michael Barnes.

In Los Angeles, conservative television commentator Bruce Herschensohn said Tuesday he is ''very, very proud'' of his years on Nixon's White House staff as he announced his bid for the Senate seat held by Democrat Alan Cranston, who is seeking re-election.

Herschensohn, a commentator for KABC-TV in Los Angeles for the past eight years, faces nine other candidates in the GOP primary. He went from the United States Information Agency to the White House in 1972, where he served as a special assistant and speech writer until Nixon's resignation in 1974 in the Watergate scandal.

Asked if his ties to Nixon might become a campaign issue, Herschensohn said, ''If someone wants to make it an issue, they're invited. I certainly have no apologies. ... I'm very, very proud to have served him.''

Elsewhere, David T. Kenner Sr., supervisor for a Boston retailer of dental products, announced his candidacy for the Democratic nomination to Boston's 9th Congressional District seat, held by Rep. Joseph Moakley.

At least two candidates dropped out of races for U.S. congressional seats Tuesday.

Rep. David S. Monson, R-Utah, quit the race for the 2nd District seat he won in 1984, saying politics were detracting too much from his family life.

Monson, 40, a former state auditor and lieutenant governor, said an apparent lack of support from his party had not been a major factor in his decision. Several Republicans have expressed interest in running for the Salt Lake City seat. Former Rep. Wayne Owens is considered the likely Democratic contender.

In Thousand Oaks, Calif., Assemblyman Tom McClintock pulled out of the 21st Congressional District's Republican primary race. He said he believed challenger Tony Hope, the adopted son of entertainer Bob Hope, would have won by outspending him during the campaign.

McClintock and Hope were vying for the seat held by Rep. Bobbi Fiedler, R- Calif., who is running for the U.S. Senate.