It was the kind of happy timing a politician lives for: he makes the cover of Time magazine at the same moment he is a center of national attention with a major bill on the Senate floor.

And that is how it was last week for Sen. Jesse Helms (R-N.C.), except for a small detail. He didn't make hay; many senators and farm groups say he made hash of the farm bill.

The week began with his owlish face fronting Time, which celebrated his magnetic pull as a paladin of the new conservatism. Five days later, he was slouched in a back-row seat of the Senate, the committee he chairs was in serious disarray, and his place down front as chief persuader and traffic cop was occupied by another senator, Robert J. Dole (R-Kan.), trying to save the day.

Magazine images notwithstanding, it was a rocky time for Helms, a man to whom considerable powers are attributed, undergoing his first big test of leadership as a chairman by trying to guide a new four-year farm bill through the Senate.

The bill was passed late Friday. The White House was happy with the measure, for it turned out better than the president might have hoped, but there was another side to this story.

Jesse Helms had problems. His style had turned members of his committee resentfully against him, the farm coalition had come apart in an unprecedented way, the bill he shepherded bore little resemblance to what he began with and, in a certain sense, his image as an all-powerful political orchestrator seemed subject to some revision.

"Old Hummin never would have let this happen," said a Republican member of Helms' Agriculture Committee. "But to be fair, Hummin never had to deal with a budgetary element like Jesse did this year."

The reference, of course, was to Herman Talmadge, the Georgia Democrat who chaired the committee until his defeat last year. Talmadge was acknowledged to be a master at putting together coalitions and keeping logs of accommodation rolling at a furious but felicitous pace.

What is different this year, with Republicans in control of the Senate, is that Helms inherited an extraordinary burden--chairmanship of a major committee faced for the first time in its history with producing a farm bill while exercising budget restraint.

His Republican president wanted sharp cuts in farm programs, and it fell to Helms, a self-proclaimed economizer and Reagan supporter, to control a committee of senators eager to protect traditional programs, costly or not.

Under pressure from the administration, Helms supervised a last-minute rewrite of the bill his committee had turned out in late spring. That procedure, allowing Agriculture Secretary John R. Block into the closed-door meetings, offended some members. "It was foolish," said a Democratic senator. "Doesn't he understand a separation between the legislative and executive branches?"

More resentment boiled up among senators who saw Helms willing to allow budgetary assaults on the dairy and grain support programs, while standing resolutely against changes in the peanut and tobacco programs--both of major interest in his home state.

"To be an effective chairman, you have to know as much as anybody about these programs and you have to take a broad view, but Jesse didn't do either," said a Midwestern Republican member of his committee. "He made it clear in the committee that all he really cared about was peanuts and tobacco and if he was not satisfied with those two he was willing to see the whole bill go down."

That attitude, in the view of some, helped set the stage for the commodity-against-commodity atmosphere that developed during debate, a new phenomenon among farm-state senators who have traditionally supported each other's interests.

It also helped propel members of the Agriculture Committee into positions that went counter to Helms' wishes. Sen. Richard G. Lugar (R-Ind.), for example, led a partially successful effort to revamp the peanut support program.

Sen. Rudy Boschwitz (R-Minn.), feeling abandoned and undercut by his chairman, battled to return dairy supports to the form adopted originally by the committee but then renounced by the administration. Did he feel his chairman had failed to defend the earlier committee position adequately? "No comment," said Boschwitz.

As unraveling of the old commodity alliances became more apparent during the debate, Dole--respected and knowledgeable on farm programs--increasingly took over direction of floor activities to keep the bill on track. And Helms increasingly was staying to one side or staying off the floor.

Tobacco survived three separate challenges, but on the last, a 41-to-40 vote to table an amendment by Sen. Thomas F. Eagleton (D-Mo.) to alter the tobacco program, only help from the GOP leadership saved Helms. Time for the roll call was extended and a tie finally broken when Sen. Arlen Specter (R-Pa.) was persuaded to change his vote to put Helms over the top.

Helms, according to other senators, and Sen. John P. East (R-N.C.) hurt their cause when they made cutting personal remarks during the August recess about Eagleton and Rep. Frederick W. Richmond (D-N.Y.). Word of the personal attacks circulated quickly around the Senate, which takes civility seriously, and some viewed the votes against tobacco as votes against the two North Carolinians.

It left a bad taste, and senators critical of tobacco are planning new assaults on the program through appropriations measures.

All in all, not a good week for Chairman Jesse Helms.