With late polls showing him closing the gap on favored Ronald Reagan in Tuesday's Florida primary, George Bush today scrapped a planned series of anti-Reagan ads and instead decided to come back Saturday for an intensive two-day sweep of the state.

The fast-breaking developments left the Bush campaign upbeat but confused -- with state campaign chairman Tom Kleppe giving reporters information that was contradicted within hours by Bush's national campaign manager, James A. Baker III.

Bush left here at midday after telling an airport rally he was encouraged by the trends in the state. His schedule at that point called for him to be back only part of Sunday.

But by late afternoon, while Bush was completing a last visit to South Carolina on the eye of its Saturday primary, aides had tallied the results of their latest canvassing and decided he had a chance to make what Baker called "a strong showing" Tuesday against Reagan. They canceled a long-planned fund-raising trip to New Jersey and began patching together a schedule in Florida for Saturday.

The hope in the Bush camp is that he can do well enough in Florida, not only to bolster his chances in the March 18 Illinois primary but also, as one official said, "to send a message" to Gerald Ford that the former president is not needed as a stop-Reagan candidate.

The decision to bring Bush back to Florida was made on the basis of telephone canvassing results showing a six-point swing in Bush's direction between Tuesday, when he won the Massachusetts primary, and today.

A pre-Massachusetts poll by the Bush organization had shown him trailing Reagan in Florida by 12 points.

The same trend is confirmed in a "before-and-after" poll that is to be published Saturday by the St. Petersburg Times and three other papers. That survey showed that, before Massachusetts, Reagan had been on his way to an easy win over Bush in Florida, but that voters interviewed since Bush edged John B. Anderson and Reagan in Massachusetts were shifting enough support to suggest a "very close" contest between Reagan and Bush.

Along with the decision to bring Bush back to Florida was the ruling by Baker to cancel planned radio and newspaper ads attacking Reagan's abortion and equal rights views and his "inexperience" in foreign affairs.

The planned radio ads, harsher than anything Bush has thrown at Reagan in their campaign so far, compared the former California governor to President Carter, a former governor of Georgia.

"Today," the script read, "we are being asked to support another former governor with no experience in foreign policy and no real understanding of the dangers we face in the decade of the 1980s. Can we afford to make the same mistake twice?"

Bush's Florida campaign chairman, Kleppe, told reporters the ads were scheduled to have started this morning but were withdrawn because David Keene, Bush's national political director, thought the narrator's voice was "too harsh." New versions of the same ad, with a different narrator, were being distributed, he said.

But Baker said a few hours later that he had ordered the ad killed because it was "too harsh and negative," and also had vetoed plans by Kleppe and the Florida Bush organization to run newspaper ads this weekend charging that Reagan had "flip-flopped" on the issues of abortion and equal rights for women.

The ads were planned by Kleppe to offset a continuing assault on Bush by conservative groups over his positions on gun control and abortion and his past membership on the Trilateral Commission, a private organization devoted to closer economic links between North America, Western Europe and Japan.

Kleppe said the anti-bush ads, paid for by the Florida Conservative Union and similar groups, have had "our phones ringing off the hook, and we're going to change things around and let Ronald Reagan's phones ring off the hook."

But those plans were vetoed by Baker and the national staff when they found evidence that Bush was closing on Reagan, despite the assault.

Kleppe told reporters he believed the conservative groups' anti-Bush ads were "inspired by" or "prompted by" the Reagan organization, which would be a violation of federal election laws. But that charge was strongly denied by Herb Harmon, Reagan's state campaign coordinator, and by Mike Thompson, the pro-Reagan chairman of the Florida Conservative Union and signer of the $25,000 newspaper ads on trilateral Commission issue.

The commission was founded by New York banker David Rockefeller and its members include business and political leaders from Japan, Europe, Canada and the United States. Both Carter and Bush are former members.