Could it be that the political clout of a seat on the House Appropriations Committee isn't what it used to be?

Two weeks ago, Rep. John P. Murtha (D-Pa.), the committee's ninth-ranking member and head of its defense subcommittee, barely squeaked by a primary challenge and won renomination to his ninth term. Now, the man just ahead of him in committee seniority, Rep. Bill Alexander (D-Ark.), faces an equally serious test in Tuesday's Arkansas primary.

Alexander, an 11-term House veteran, is being pressed hard by Mike Gibson, Osceola city attorney, who has reported raising $313,000 for the race -- only $105,000 less than the incumbent. Gibson's television spots assail Alexander for supporting the congressional pay raise, for winning 82 percent approval from the American Civil Liberties Union and for voting to finance "obscene, anti-religious works of art."

He also questions why Alexander is not at least a subcommittee chairman after 22 years in Congress and why the only bill bearing his name that has become law in the last 10 years commemorates Dutch-U.S. friendship.

Alexander has replied that his position as the second-ranking Democrat on subcommittees controlling military construction and economic development funds has meant millions of dollars in benefits to the poor district. Several members of the Congressional Black Caucus have campaigned for Alexander, and observers say that his chances of surviving Tuesday may depend on his ability to retain the solid black support he has enjoyed in the past.