Last Monday in Missouri President Carter junked the last half of a fairly standard speech on farm policy to say instead that inflation will never be curbed unless Congress can break free from the grip of "the special interests."

The next day, Carter's secretary of agriculture told a group of reporters in Washington that the administration plans to retaliate against Democratic congressmen who persist in taking "cheap shots" at the president.

Two days later, Carter became the first president in more than a century to veto a major weapons authorization bill. He told a nationally televised news conference he wished he had vetoed more bills in the past and that he will not hesitate to veto others in the future.

That night, the president summoned members of the congressional natural gas conference committee to the White House for what apparently was an old-fashioned session of arm-twisting and trading aimed at salvaging the natural gas section of the administration's energy program.

These four, seemingly unconnected developments form part of a pattern that has begun to emerge from Carter's beleaguered White House in recent weeks.

The president and his aides are embarked on a still cautious but deliberate effort to revive Carter's congressional relations image, presenting a more assertive president who, in the words of one aide, is telling Congress "to put up or shut up."

No one in the White House is prepared to say that Carter, so successful in 1976 as the Washington "outsider," is about to repeat history and campaign, in effect, against a Congress controlled by his own party. There is not even agreement among White House aides on the extent to which the president should or will become more openly critical of Congress.

But it is clear from interviews with White House officials that, with time running out on the 95th Congress, with many of his key bills still bogged down and with the level of personal sniping at him by members of his own party increasing, Carter has decided he must act to counter his image as a weak chief executive who is being pushed around by Congress.

"There is a consensus here that we have no choice at this point," one senior presidential adviser said. "We can not allow a situation to continue in which people are free to blame the president for their own shortcomings."

According to the White House view, it is Congress, much more than the president, which should shoulder the blame for the legislative failures of the past 19 months. Much of what Carter promised in his campaign remains stalled in the halls of Congress - the list includes the energy legislation, welfare "reform," overhauling the civil service system, enacting tax cuts and revising the tax code.

But it is also clear to those around Carter that Congress is not being blamed. The president's slide in popularity is directly related to the perception of him as infeffective. It is an image that is feeding on itself.

What is particularly aggravating to Carter's aides is what they consider the rising tide of "personal sniping" at the president by congressional Democrats.

Earlier this year, the White House issued orders that the administration was to use all of its resources to help the election campaigns of Democrats. Cahinet officials and White House senior staffers were dispatched to appear at campaign and fund raising events. It was part of the White House's great effort at "accommodation" with Congress.

"I went to two or three places on weekends to raise money," one official recalled. "And then some guy who had gotten some of the money pops off in his local newspaper about the incompetence of the White House senior staff. It just burned me up."

Because of such incidents, this official said, Agriculture Secretary Bob Bergland's comments about retaliation "reflected the general attitude" in the White House even if Carter publicly disassociated himself from them.

"There is a lot of resentment here and a sort of feeling of patience at an end with some of this stuff," he said.

"The accommodation didn't work," another aide said as he spoke of an "attitudinal change" in the White House, born of "increasing frustration" over attempts to reach accord with Congress.

But just what Carter will do to change the situation he finds himself in is not clear. There will probably be more vetoes and increased, if generalized, criticism of Congress. But the president's options are limited. It is a Democratic Congress and he will be campaigning for many of its members this fall.

"I think he's going to avoid stridently attacking Congress and accusing them of being a 'do-nothing' Congress because that might be counter-productive," one aide said. "They might dig in. But he does want to ge across the idea that the cumulative effect is to obstruct."

The president's speech last Monday to the Midcontinent Farmers' Association in Columbia, Mo., may have been a preview of this approach. In it, Carter did not attack Congress directly. Instead, he charged that "special interests" are blocking his legislative proposals and feeding inflation. But the implication was clear - without strong, countervailing public pressure, the president was saying, Congress inevitably will cave in to "the special interests."

"The thinking from Carter was that it is time to prepare the way for a tougher line with Congress," said one aide of the decision to junk a prepared speech on farm policy and deliver the attack on "special interests."

According to this official, the hope is that an increasingly critical line toward Congress this year will bring a few immediate successes this year and pave the way for a much more productive legislative session next year. How the president fares with Congress next year, the last before the 1980 elections, "is viewed as the key to (Carter's) reelection success," he said.

But even as the White House launches an effort toward more aggressive congressional relations, there are questions about whether the president really means it this time.

For 19 months, Carter has been groping for the right approach toward Congress. He has been "firm" and "tough" at times, then lapsed into long periods of "accommodation." Even White House aides aconcede that the approach has been inconsistent, but they say Carter has learned his lesson.

They are not convinced of that on Capitol Hill. One of the Democrats White House officials complain about is House Majority Whip John Brademas (D-Ind.), whom they accuse of taking a series of "pot shots" at the presiden since Brademas unsuccessfully opposed the administraion's effort to lift the Turkish arms embargo.

After Brademas eard of the complaints, he raised the subject with Carter last week at a White House meeting with congressional leaders. He was assured by the president that nothing could be further from the truth, that Brademas was considered one of the administration's staunchest supporters.

As for Bergland's threats about retaliation, Carter tols the group, he had never even discussed such a tactic with the agriculture secretary.

It was said they had a good laugh about the meeting back on Capitol Hill.