Batoff, a leading Democratic national fund-raiser for almost two decades, said he would "do some soul-searching" and might end up "just staying out of it" through the general election campaign.
He planned to concentrate his efforts on fund-raising for Senate Democrats.
Batoff said he had been counseling Harkin recently to drop out. Harkin left the race without endorsing anyone but promising strong support to the Democratic nominee against President Bush.
Batoff said he viewed Bill Clinton as "clearly the favorite" but was uneasy about the Arkansas governor. He attributes the success of Paul Tsongas to "a resistance to Mr. Clinton. He is not the clear choice, which is trouble for November, big trouble."
Batoff said he was concerned that Clinton had won Southern primaries simply by pulling automatic Democratic constituencies including blacks and liberals. Tsongas, even while losing, attracted more conservative Democrats, he said: ''the people you need to beat Bush. They're the Bush voters."
Harkin had campaigned as an unrepentant old-style liberal with strong early backing among organized labor.
But his harsh style and lack of specific solutions led to erosion of support. His only clear-cut victories were in caucuses in his home state of Iowa and in sparsely populated Idaho.