The Democratic caucus on the MX missile was called ostensibly to discuss strategy for the upcoming debate on the MX. But in short order, and for good reason, it turned into a tribunal on the character of Rep. Les Aspin of Wisconsin, the keeper of the "Peacekeeper."

Liberal Democrats are furious with the agile Aspin, who they say snookered them into supporting him in his coup against Mel Price of Illinois as chairman of the Armed Services Committee and then welshed on his word. Aspin, his glummy critics agree, provides the margin in the tight fight. The anti-MX forces are 10 votes short.

Edward J. Markey (Mass.), a vociferous MX foe, was the first on his feet on the real topic of the day. He told the closed dorr meeting of a conversation he had with Aspin last January in the back row of the House chamber. Aspin is highly regarded for his grasp of technical detail, but has been suspect since his slithering on the MX, opposition to which is official Democratic Party doctrine.

"I asked him if he oppose the MX," Markey told his colleagues. "He told me he would have to find the means to harmonize his '84 position with the present status, but that he would vote against it."

Rep. Fortney Stark (Calif.) spoke up. "I got the same commitment from him." Several other voices from the floor said, "So did I."

Markey went on to detail Aspin's 1984 history on the MX. The House was within a whisper of burying the MX. Aspin, an ardent advocate of the Scowcroft Commission, which deplores the weapon but wants it produced, had been engaged in heady arms control talks with the White House. Aspin said that if it came down to a question of 21 missiles verss zero, zero would win -- and promptly stitched up a compromise that turned out to be a stay of execution.

Under his arrangement, funds for the missile would be "fenced" and could be released only if the Soviets failed to return to the bargaining table and the president certified that they were bargaining in good faith. Aspin's amendent failed and one from Democrats Charles Bennett of Florida and Nick Mavroules of Massachusetts, which required Congress to make a good-faith certification, was passed.

The effect of each amendment was the same: As long as the Soviets were found to negotiate sincerely, the MX was forzen.

Now, however, Aspin is saying that the money should be spent to show the Societs in Geneva that we are "serious."

Barney Frank of Massachusetts has a sardonic summary of the Aspin position. "We used to be told we need it because we were not having talks with the Russians; now we are being told we need it because we are having talks with the Russians."

When Markey finished speaking, Les AuCoin of Oregon took the floor. He accused Aspin of being "a private contractor" with the White House and of "deciding on your own what is best for the Democratic Party."

Democrats, AuCoin said, do nothing to counter the impression of being "soft on defense" by voting for weapons systems that are "inherentky bad and encourage the Soviets to match us with equally bad and equally dangerous first-strike weapons."

Howard Wolpe of Michigan rose, and, with some emotion, told of his pledge from Aspin, who was slumped down in a chair and was, according to one spectator, "looking like a wounded puppy."

"I had a promise," Wolpe said. "I feel betrayed."

Aspin came forward in hisown defense. The trouble with the MX resolution being offered is that the speaker has forbidden any amendments.

"Don't try to pin this on Tip," shouted Mary Rose Oakar of Ohio.

As for his promise, Aspin advised his peers to ask "other members for their interpretation of what I said."

"I don't care what you said to others," Markey shit back. "I know what you said to me."

Aspin said that because his amendment failed, he was not bound by his previous statements on the subject.

Only two Democrats spoke in favor of the MX, Sam Stratton of New York and G.V. Montgomery of Mississippi. They had little to say. The big irony in the litte drama was that the presiding officer was Charles Bennett of Florida, an old-fashioned and gentlemanly convert to the MX opposition, who was passed over ub favor of the yuppie Aspin.

The Democratic Caucus was first used as an anti-MX weapon almost two years ago, when a freshman, Jim Bates of California, ruffled feathers by demanding one to roast the House leadership, four ofwhom voted for the MX. After a heated venting, mostly aimed at Majority Leader Jim Wright, things changed. The last holdout, Deputy Whip William Alexander of Arkansas, fell into line last Tuesday and in the House Appropriations Committee voted against the Peacekeeper for, he said, budgetary reasons.

No one expects his two hours in the woodshed of his peers to make Aspin repentant or even abashed. But at least, said one liberal, "We didn't make his day."