When President Carter sent shockwaves through the Southwest's political establishment Oct. 13 by warning of an infamous oil industry "ripoff," it climaxed the disillusionment of one influential Texas Tory Democrat who last year greeted Jimmy Carter's candidacy with enthusiasm.

"I give up on him," this important figure told us. Prepared to sell his fellow Tories on the virtues of the Panama Canal treaties, he now opposes it himself. To this Texas politician, Carter has branded himself "just another ultraaliberal even if he is from the South."

We found that attitude prevalent among Democratic politicians we questioned in the oil-producing states of Texas and Oklahoma the week after the President's "sipoff" charge. Those presidential advisers who see anti-Carter resentment here limited to big oil do not appreciat the hostility among moderate-to-conservative Democrats who last yeart embraced Carter as one of their own.

That the President's difficulties in this region stem from more than oil policies can be seen in the disaffection of three early Carter backers: Oklahoma Gov. David Boren and Gov. Dolph Briscoe and Lt. Gov. William Hobby of Texas. Their stories possibly point to reasons for the President's national decline.

Hobby: An admirer of Carter since visiting him in 1971 to observe his reforms as governor of Georgia, the widely respected lieutenant governor has no channel to the administration. He has been unable, for example, to contact Secretary of Energy James Schlesinger. Hobby says he reacted with "sorrow" to Carter's blast at oil, but his private reactions are markedly stronger.

Briscoe: He was friendly from the start toward the Carter candidacy and risked his own prestige to carry the state for Carter last November. The phlegmatic governor is genuinely outraged by the President's denouncing Texas politicians for supporting natural-gas deregulation that had been promised by candidate Carter.

Boren: The aggressive 36-year-old governor of Oklahoma represents a highly dramatic change of relationships with the President. The first governor west of the Mississippi to back Carter for President, Boren elicited the now-repudiated pledge for gas deregulation.

Boren was completely cut off from the White House before the energy program was unveiled last April, his telephone calls unanswered. Since then, he has had only one personal contact with the President: An astonishing - and fruitless-appeal from Carter for support for the Panama Canal treaties. At no time has the President explained to the governor, much less apoligized for, breaking his word on deregulation.

Thus, the President's Southwestern slump is caused not only by his stand on oil but also how he has taken that stand. The President has implied that anybody opposed to him is more interested in appeasing the greedy oil companies than in furthering the national interest-a view not likely to soften the blow to his erstwhile supporters.

Nor is resentment limited to politicians allied with the giant oil corporations, as the White House supposes Govs. Briscoe and Boren to be. Texas State Land Commissioner Bob Landis Armstrong, a liberal and Carter's Texas campaign chairman, opposes both the substance and the rhetoric of the Carter energy program. Needless to say, his advice has not been asked.

Even more striking is Robert A. Hefner III of Oklahoma City, an independent oil producer and political foe of both the big corporations and Gov. Boren. While attacking Boren as too closely allied with Phillips Peroleum, Hefner is no less outraged than the governor over Carter's position. The President's "ripoff" statement is "a the - atrical attempt to gain emotional support," Hefner told us.

In fact, independent producers are perhaps mor anti-Carter than the oil giants the President chastises. The independents believe that the Carter program, with its emphasis on government regulation, could eventually doom them and unwittingly limit oil production to a few big hands. That sentiment has poisoned the political well, far beyond just oil-industry executive suites, for Carter in Texas and particularly in Oklahoma (where Boren privately tells friends the President could win no more than 25 per cent of the vote today).

Even with this disagreement over oil and unhappiness with his positions and illegal aliens, the President could restore his position in the Southwest - if he began rebuilding burned bridges to the Borens, Briscoes and Hobbys. The alienation of the Southwest is no less a matter of decaying personal relationships than of unpopular policies, perhaps a hint of what has gone wrong with the Carter presidency.