The Disgust of the president's most prominent endorser in this economically ravaged former steel city that gave him a 1978 landslide reflects a bitterness toward Jimmy Carter through industrial northern Ohio threatening him in the June 3 primary.

While Youngstown's Democratic organization is aligned with Sen. Edward Kennedy, Carter's Ohio managers point to Mayor George Vukovich as the president's man here. But, to use Lenin's phrase, the mayor supports Carter as a rope supports a hanged man. "I wouldn't say I was really supporting him," Vukovich told us. "Between you and me, I'm disgusted."

His disgust stems from a sense of betrayal and neglect that is endemic here. The complaint of Youngstown Democrats from the mayor to the lowliest precinct worker. Carter has repaid Youngstown for its huge plurality in 1976 with neglect; we will repay him in kind on primary day. That the president has nearly enough delegates for nomination means nothing here.

Carter faces somewhat lesser resentment in Cleveland and Toledo, where (as in Youngstown) the Democratic county chairman back Kennedy. He also could lose Akron, Dayton and perhaps Columbus. That adds up to a possible Kennedy upset in Ohio, which, if coupled with Kennedy victories in California and New Jersey the same day, could create an unhealthy climate for the president at Madison Square Garden in August.

Rural southern Ohio, whose small towns are subjected to tireless visitations from Chip Carter, will give the president the same 60-percent-plus vote he enjoyed in neighboring Indiana. But this area does not have nearly enough Democratic voters to overcome a Kennedy sweep in the north.

Accordingly, Carter's campaign last week began the remorseless repetition of anti-Kennedy television commercials that aborted the senator's rise in Pennsylvania. The difference in Ohio is a spirit-sapping recession that began long before the national slump. Unemployed steel, rubber, and auto workers form a dagger pointed at Carter's throat. In Youngstown, where failure to replace the now-departed basic steel industry has reaped despair, unemployment is around 12 percent and rising.

Just four years ago, this was Carter country. When he needed Ohio to pin down his 1976 nomination, the 19th Congressional District gave him 60 percent (to 14 percent for second-place Frank Church). The district delivered him the same 60 percent in November against Gerald Ford, the third-largest Carter victory margin in the nation. But he has never visited northern Ohio as president.

Don Hanni, the tempestuous Mahoning County Democratic chairman, two years ago pounded the table over cheeseburgers in the White House mess to demand help for this stricken area. When no help came, Hanni endorsed Kennedy even before he ran. While postponing formal organizational endorsement to avoid undercutting his candidate for sheriff, Hanni will pass the word for Kennedy a few days before the primary. John Knapp, a precinct committeeman who owns a saloon called the South Side Civic Club, told us, "Hanni is my godfather," and he awaits his direction. But he added that "the boys" who drink at his bar are anti-Carter anyway. Indeed, a night spent among Democratic activists here indicates Hanni will not have to push very hard.

At a Democratic candidates night rally, not one hand out of 135 people present was raised when we asked for Carter supporters. A meeting of 6th Ward committeemen split 4 to 1 against Carter. Out of 24 committeemen at a 5th Ward meeting, 22 backed Kennedy. "Carter don't even know we exist," complained one 5th Ward committeeman.

That is precisely the complaint of Mayor Vukovich, who as court clerk in 1976 was an early booster of Jimmy Who. "Since then," he told us, "they haven't done anything for us." Vukovich's 11-page letter to the president in mid-March, detailing the torment of Youngstown went unanswered. The last straw was the icy stare from federal bureaucrats when Vukovich tried to restore $3.5 million in desperately needed urban grants denied for non-compliance with regulations. The neighboring town of Warren won similar grants, after which its mayor, Daniel Sferra, endorsed Kennedy.

"The president has the Monopoly board in this game," one of Carter's Ohio operatives told us, "and whatever happens, he's going to be around to help and punish at least until next January." But for Youngstown, the carrot and the stick have long since lost all validity.

These Democratic activists say they are for "ABC" -- Anybody But Carter -- and are lukewarm about Kennedy. Could this Democratic bastion embrace Ronald Reagan? All the party people say it is possible. Jimmy Dunne, district leader of the 6th Ward, told us the rest of his family would vote for Reagan in a Reagan-Carter choice. The threat posed here to the president will not end June 3.