Sen. Ernest F. Hollings (D-S.C.) said yesterday that he and other critics of the MX missile now have enough Senate votes to block production of the costly and controversial new weapon.

Asserting that Congress got a "whole new stop-look-and-listen message" from the voters last week on defense spending, Hollings told a news conference that eight Senate Democrats who were reluctant to vote against the MX before the elections are prepared to do so now.

In a pre-election vote on stopgap funding for the government, Hollings lost 50 to 46 when he urged the Senate to knock out $988 million to start production of the new intercontinental missile. The House managed to knock the money out in conference anyway, but only temporarily.

Since he now foresees eight or more post-election switches, "I'm absolutely convinced . . . the MX is dead from the standpoint of any production," Hollings said.

A Senate Republican leadership source questioned Hollings' count but conceded an anti-MX vote was possible in light of strong post-election sentiment for greater restraint in defense spending.

Hollings said he favors going ahead with $2.4 billion for continued research and development for both the missile and its basing system in hopes the money could be used to devise a smaller, more mobile weapon and a basing system that would be less vulnerable than the "Dense Pack" basing system now under study by the administration.

The administration has said it will decide on a basing plan by Dec. 1, and Hollings said that "Congress isn't going to approve any kind of Dense Pack," under which the missiles would be clustered short distances from each other.

Hollings said he will seek to cut out the MX production money in either the defense appropriations bill or in a second stopgap funding bill if the defense money bill gets bogged down in the lame-duck session due to start Nov. 29.

In any case, a Senate vote against the MX would be interpreted as a powerful signal of what many congressional leaders describe as a growing sentiment for moderation of the administration's huge military buildup plans, especially in light of projected annual deficits of up to $200 billion over the next few years.

The Senate Appropriations Committee has included the $988 million for MX production in its defense money bill. The House Appropriations subcommittee on defense is scheduled to begin work on its version of the measure next week, and subcommittee Chairman Joseph P. Addabbo (D-N.Y.) has targeted several big weapons systems, including the MX, for possible reductions or elimination.

Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) has listed a defense appropriations bill on the agenda for House action during the lame-duck session. But there is some doubt in Congress that the defense bill can be finished before Congress quits for Christmas, meaning the Pentagon would have to be financed again in an omnibus measure.

In either form, defense spending is a target for cuts under Democratic plans to finance an emergency program of public works jobs and housing subsidies at least in part by cuts in defense.

The House Democrats are talking in terms of trimming defense spending to allow no more than a 5 percent real (after-inflation) growth in military expenditures. In contrast, Hollings, who only a few years ago was in the forefront of the defense buildup forces in Congress, is talking now of limiting defense increases to 3 percent as part of a general deficit reduction program.

At his news conference, Hollings said he will also seek to scrap the B1 bomber program, which congressional budget experts estimate will cost up to $40 billion. But he said he was less optimistic about succeeding on the B1 than he is on the MX.