Republican presidential candidate John B. Connally today charged that President Carter has "conned" the American people on the hostage situation in Iran and used it for his own political benefit.

In one of his harshest attacks to date on the issue, Connally accused the Carter administration of deliberately misleading the public on prospects for release of the hostages before the U.N. commission was established to investigate alleged human rights violations by the former shah of Iran.

"We've been conned by that stacked-deck commission that's been set up solely for the purpose of humiliating and ridiculing the United States," the former Texas governor said in an interview.

Connally picked up today where George Bush left off Sunday. Campaigning in Massachusetts, Bush also accused Carter of misleading the American people about the hostages and called on the president to tell "the truth behind the facade of diplomatic activity."

Connally, stumping across the snow-covered hills of South Carolina, said events have shown there was no linkage between the panel and release of the hostages.

"And if there wasn't any linkage, we've been conned, and American people have been conned," he added.

Connally, struggling for his political survival in Saturday's South Carolina primary, made his comments in an interview between stops on a six-city bus tour through the central and northwestern part of the state with Sen. Strom Thurmond (R-S.C.).

Earlier, he told a college audience at Lancaster that Carter was using the Iranian crisis to further his reelection bid. "You ask yourself in whose political benefit it is that the hostages stay imprisoned," Connally said. "They've been there a long time."

His statements are indicative of the fragile bipartisan support of the administration's foreign policies, and the frustrations that Connally and other presidential candidates feel over the way Carter's popularity has skyrocketed since the seizure of the American Embassy Nov. 4 and the Soviet invasion of Afghanistan.

Ronald Reagan, front-runner for the GOP nomination, expressed a similar opinion campaigning in Tampa, Fla., Friday. "It appears President Carter is trying to ride the Iran crisis back into the White House," he said. "I think the United States has already been greatly humiliated by those people being held there so long."

"Let's not assume that no hostages have been killed because he [Carter] is doing a good job," Connally said at one stop today. "Why were they hostages in the first place? Because of him.

"Why should a man be rewarded for what he's not done?" he asked later, adding, "He's profiting from the very thing he caused."

Connally said two people, the Ayatollah Khomeini and Leonid Brezhnev have "completely changed the political climate of the country during the last four months. Frankly, I don't want our next president to be picked by either of those men."

He also charged that Carter's trade and grain embargo against the Soviet Union was "largely election gimmickry." He charged that shipments of high technology computers are still being made to the Kama River truck plant. Trucks made in the plant, he said, are being used for "personnel carriers and other weapons of war" in Afghanistan.