Fund-raising for Jimmy Carter's reelection has gone bone dry the last two months, an experience unprecedented in the modern presidency that could rule out an effective 1980 Carter campaign.

President Carter's money appeals are rejected by sources on which he had depended: The Jewish community, elements of the oil industry, businessmen particularly dependent on government decisions. Washington lobbyists have stopped tapping clients' bank accounts. Selling tickets to Carter fund-raisers is hard labor.

This reflects not only the presdident's deteriorating political condition but practical campaign problems. His present cash-on-hand is reported at $947,350, but the easy money has been raised. Nobody can imagine how to raise the additional $4 million that ought to be there by January for Carter to collect enough federal matching funds to run the kind of pre-convention campaign he needs.

Heavy early funding is necessary because of the prospect Carter will lose early primaries, whether or not Sen. Edward M. Kennedy opposes him. That means Carter's only chance will be slogging it out in every primary, which, indeed, is his plan. For that reason, knowledgeable supporters and even some administration officials privately talk about the possibility of his empty war chest forcing him out of the race.

None of this seemed imminent as summer began with $1.5 million raised for Carter. The first chill came when ticket sellers encountered massive sales resistance for Carter's $1,000-a-plate kickoff dinner at the Washington Hilton Hotel on June 25. Although the $174,214.45 net profit was close to the original target, it was reached only after prodigious effort.

The chill became a freeze in July. Much of the Jewish community often estimated at 70 percent of Democratic presidential fund-raising) was alienated by Carter's Mideast policy. More generally, clients began telling their lobbyists that they simply did not care to help Carter, whatever effect that might have on closing Washington's doors to them.

The temperature went frigid with Carter's ill-conceived Cabinet shake-up. Apart from generally numbing his support, it had one unintended result: shutting off substantial commitments from the oil industry. Dr. James Schlesinger had grown steadily more popular within the industry, particularly among larger independent producers. When Schlesinger fell as secretary of energy, the president lost that oil money.

By mid-July, even the fund-raisers were bailing out. It was no accident when one lobbyist, a veteran of Democratic wars who had been plucking his clients for Carter, missed an August meeting of the president's business supporters. He had decided he could no longer press his clients to a lost cause. If he tries to extract money in the future, it will be for Kennedy.

Few other businessmen or lobbyists are switching to Kennedy. Even so, Teddy Kennedy does not arouse the pervasive fear of Robert F. Kennedy that helped keep money pouring into President Lyndon B. Johnson's war chest until the moment of his withdrawal.

One reason is that conservative Democratic businessmen who showered money of LBJ in 1968 -- and presumably would prefer Carter over Kennedy this time -- are intent on securing the Republican nomination for ex-Democrat John B. Connally. Like many of their Republican brethren, they consider Connally certain to be the next president (when, in fact, he remains a long shot).

Evan Dobelle, Carter's chief fundraiser, told us ingenuously that the president encounters no greater difficulty than any other candidate coping with post-Watergate restrictions. Indeed, there is evidence the Carter political team does not recognize the president's plight. Thus, there was no response at the business group's August meeting when two famed Democratic lobbyists declared -- only partly in jest -- they could raise money only if Treasury Secretary G. William Miller was made available to them, for two days each, to see all their clients.

They did not want Rosalynn Carter, whose fund-raising forays make more news than money. The only two Carter VIPS able to crack the money freeze are Miller (considered by the White House inappropriate for such grubby work) and Ambassador Robert S. Strauss (who has his hands full in the Mideast).

Glum Washington lobbyists who have stuck with Jimmy Carter through the bleak summer of '79 have come to believe Kennedy will end up in the race. If that perception spreads nationally, it could conceivably generate funds for the president's defense. But if the course taken in Washington is duplicated, fewer dollars than ever will go into the Carter war chest -- so few that he might consider withdrawing because of unprecedented inability by an incumbent president to finance his campaign.