Florida's Democratic Party chairman reversed himself yesterday and abandoned his party's planned lawsuit aimed at knocking John B. Anderson's name off the November ballot, fearing that the suit would have created a sympathy blacklash for the independent presidential candidate.

Charles Whitehead, a leader of the state's pro-Carter forces, said his change of heart came mostly because of two weekend polls -- one by the Democratic Party, the other by newspapers -- showing that Anderson's candidacy was declining of its own accord in Florida.

Whitehead conceded that he had come under considerable pressure yesterday after published reports disclosed the party's plan to file the suit, and that some Carter campaign officials in the state had not been pleased to read the accounts.

On Sunday, James D. Whisenand, a Miami attorney representing state Democratic Party officials, told The Washington Post that he would be filing the anti-Anderson lawsuit yesterday on behalf of the state party's executive committee.

Whisenand said that Whitehead had approved the filing of the suit.

Whitehead maintains, however, that this was a "tentative" decision. In an interview, he also initially denied that he had polled the party's central committee and that its members had favored the filing of the suit.

But after the party's vice chairman, Hazel Evans, confirmed that she had telephoned central committee members at Whitehead's request last week, Whitehead conceded that he had requested the polling. Evans said the central committee had agreed to back the filing of the suit.

On Sunday, a Florida poll by four state newspapers showed that President Carter and GOP nominee Ronald Reagan were deadlocked in support in Florida, with 28 percent each, while Anderson had 8 percent. Whitehead maintained that another poll conducted for the party produced similar results, which were given to him Sunday.

"We began to feel that we didn't want to provoke a sympathy vote for Anderson with our suit," Whitehead said.

Carter's Florida coordinator, Jay Hakes, said he had urged Whitehead not to proceed with the suit. "Why help him revive his candidacy by making a martyr out of him?" Hakes asked in an interview. And he added:

"You know how campaigns are. We decide to do a helluva lot of things that just don't get done."