The spectacle of Jimmy Carter barnstorming through the South two weeks before the election as foe of big government and defender of the oil industry reveals that campaign manager Hamilton Jordan's victory plan is off schedule, with time running out.

The president's men are still genuinely confident that, thanks to the return of Democratic voters and, they hope, a break in the Iranian hostage situation, they will be on top Nov. 4. But they privately admit they had expected to be moving well ahead by now, with undecided voters flooding to Carter. The source of the shortfall is easily identified: the president's deteriorating southern base.

In this election, Carter could not rely on a solid South, as in 1976, while concentrating on big northern industrial states. Ronald Reagan leads in four southern states and is no worse than even in four more. As Carter campaigned in Texas, the Democratic politicians who greeted him confided that Reagan has a clear lead for this state's 26 electoral votes.

The president's southern chickens are coming home to roost. After voting in 1976 for a fellow southerner they believed shared their ideals, rural white southerners feel betrayed. In Texas and Louisiana, not only big oil moguls but small royalty owners were incensed by Carter's windfall profits tax.

No politician can abruptly alter his tone more easily than Jimmy Carter. In the oil-producing states, the windfall tax -- whose passage he boasts of so much elsewhere -- goes unmentioned. It is as if Carter's greatest energy triumph had been repealed mysteriously.

In two days of oil-state campaigning, he referred to the tax just once (without the pejorative "windfall" description): his speech to an airport rally in Waco began by promising next year to "eliminate the tax on the small royalty owners of Texas and Oklahoma and Louisiana." Here, at Beaumont and in New Orleans, he congratulated himself for oil decontrol -- a feat never mentioned by the president elsewhere.

The familiar theme of branding Reagan a nuclear-happy warmonger is muted in the hawkish South, where the president claimed he had restored the nation's defenses, which actually are considered by non-partisan experts to be in deplorable condition. Carter improbably took credit for the Trident missile, the air-launched cruise missile and the new battle tank and armored personnel carrier. Even more improbably, Carter declared: "Defenses were weakened under Republicans, but under Democrats we're putting our nation strong."

Everywhere, Carter stressed his credentials as a southern conservative. "I'm from the Deep South, from Georgia," he said in Beaumont. "My philosophy in government is probably about the same as yours. I don't believe . . . that government ought to stick its nose in the minds and hearts and jobs of people in the private enterprise system."

But two weeks from Election Day may be too late to keep Carter's southern chickens away. The deaf ear the president turned to pleas from Texas Democratic leaders to stop scapegoating the oil industry is well remembered. In the South especially, Democratic politicians truly dedicated to Carter's reelection are hard to find.

His campaign chairman in Louisiana, former governor Edwin Edwards, has assaulted Carter's energy policy and not concealed personal contempt for the president. Introducing Carter at a fund-raiser in New Orleans, Edwards could not resist calling the president "a little hardheaded." The $500-a-plate diners were there for Edwards, not Carter.

Carter's men are counting on Edwards to carry Louisiana, but insiders say he is just going through the motions to mend fences for a run at governor in 1983. The wily Sen. Russell B. Long believes Carter's organization is inadequate to carry the state, and not enough time remains to build one.

The organizational problem is even worse in Texas, where the Republican Party figures to turn out all Reagan voters. The same cannot be said for the Democrats. Although defections by local Democratic politicians are rare, so are aggressive efforts to turn out voters.

If the president cannot be reelected without carrying Texas and if prospects look grim in Texas, why then are Carter's men smiling? They are looking for Iran's release of the hostages to blot out poor organization, inadequate dedication and nearly four years of resentment. The decision of a religious fanatic in Central Asia is counted on to save Jimmy Carter's presidency from the revolt of his fellow southerners.