In a state where he has been vilified by Democrats for siphoning votes from Al Gore in the 2000 presidential election, Ralph Nader was typically unstinting in his criticisms of President Bush and Sen. John F. Kerry on Thursday, referring to the choice facing voters as one between "heart disease and cancer."

It was the final swing through Florida before the Nov. 2 presidential election for the independent candidate, who drew several hundred people to a speech at the University of South Florida here in Pinellas County, the area where he received the most votes in 2000. But even in this bedrock of his small political following, Nader's prospects are bleak.

"This year's tough for him," said Mark Kamleiter, a St. Petersburg lawyer and longtime supporter. "They've turned on him. They're so afraid of Bush."

Nader's dwindling support is no accident. Democrats and left-leaning groups have mounted a months-long legal and public relations campaign to keep the consumer advocate off ballots and otherwise minimize his impact. While independent pollsters and some Kerry strategists say Nader could still have an impact in a number of very closely contested states, Democratic officials seem less concerned that he will influence the 2004 election as they believe he did in 2000.

A survey conducted this month for the Democratic National Committee by pollster Stanley Greenberg showed Nader averaging 1.5 percent of the vote in a dozen battleground states where his name appears on the ballot, compared with about 3 percent in the summer. It also showed that most of the support Nader lost had shifted to Kerry and indicated that his remaining backers would be as likely to vote for Bush as for the Massachusetts Democrat, if Nader were not running.

Speaking about what has become known in the news media as the "Nader factor," Leslie Dach, a senior adviser at the DNC, said: "He is less of a threat to us, clearly, than he was in 2000, less of a threat than he was last summer and less than he was even a few weeks ago."

Four years ago, Nader received about 2.8 million votes nationwide, and Democrats charged that his presence on the ballot handed Bush victories in New Hampshire and Florida. Had the Republican lost either of those states, he would not have become president.

But since that time, legions of Nader's most prominent backers, including his 2000 running mate Winona LaDuke and filmmaker Michael Moore, have urged him to abandon his campaign and asked his followers to support Kerry.

Nader did not secure the endorsement of the Green Party, which nominated him in the past two presidential elections. Democrats and affiliated groups filed a series of lawsuits to keep him off the ballot in key states and starve his campaign of resources. As a result, Nader registers at around 1 percent in most national polls. In the latest sign of his struggles, he disclosed in a Federal Election Commission filing this week that he had lent his cash-strapped campaign $100,000.

Nader has qualified for at least 33 state ballots plus the District's, 10 fewer than he appeared on four years ago. Evidence of fraud on Nader petitions has been found in several states. Judicial processes related to his ballot access in battlegrounds Michigan, Ohio and Pennsylvania are still playing out.

On Thursday, Nader accused Democrats and Republicans of "political bigotry, dirty tricks and constitutional crimes" aimed at keeping him off presidential ballots.

Speaking to reporters before a campaign address at the University of South Florida at St. Petersburg, Nader said he will push for more information about efforts to undermine his candidacy until "the pus, the mucus and the ooze pours forth."

Some Democrats acknowledge privately that if Kerry loses to Bush it will be harder to portray Nader as a spoiler -- as they did in 2000, or as Republicans did with independent candidate H. Ross Perot in 1992. Polls show that the 2004 election could produce the smallest number of votes for third-party presidential candidates since 1988, when representatives of 17 minor parties earned fewer than 1 million votes.

Groups seeking to minimize Nader's impact are focusing on at least seven states -- Iowa, Florida, Wisconsin, New Mexico, Minnesota, Maine and New Hampshire -- where Bush and Kerry are in a virtual dead heat. In all of those but Minnesota, according to aggregates of nine recent polls compiled by the Web site RealClear Politics, Nader's share of the vote exceeds the thin margin separating Bush and Kerry.

"Yes, we've peeled a lot of votes away over time, but unfortunately we still have many states so close that even a half-percent could matter," said Robert Brandon, who worked with Nader at the activist group Public Citizen in the 1970s and coordinates former associates to oppose Nader's candidacy in battleground states.

In Florida, for example, where Nader received more than 97,000 votes (2 percent) in 2000, and Bush won by 537 votes, the state Supreme Court put Nader on the ballot last month after a lower court ruled him off. He is polling at about 1 percent and has campaigned often in the state.

Predicting the voting behavior of Nader supporters, pollsters say, is extremely difficult, because the sample size is so small. They tend to be younger and slightly less conservative than the voting population as a whole, and are more likely to oppose the Iraq war, said Scott Keeter, director of survey research at the Pew Research Center, which has tracked 125 Nader supporters since August.

Throughout Nader's Florida swing on Thursday, including a 45-minute live interview broadcast on the al-Jazeera television network in which Nader flawlessly delivered several answers in Arabic, he referred to Bush and his brother Jeb Bush, the governor of Florida, as "the Bush Boys and the Bush Gang." The brothers, he said, are responsible for turning Florida into a "political Disneyland."

"Disneyland should open up a new sector which is to show how unscrupulous corporatist politicians fool voters," Nader said at a news conference in Orlando.

Both candidates, he said, are "corporatist politicians" controlled by the large companies that Nader believes hold the true power in the United States. He described Bush as "a giant corporation in the White House disguised as a human being."

Nader will also campaign in closely contested Pennsylvania, Wisconsin, Minnesota and New Hampshire before the Nov. 2 election.

The conventional wisdom -- reinforced by GOP efforts in key states to provide signatures for Nader's ballot drives and assist with his litigation -- has long been that Nader's supporters would otherwise back Kerry. A Zogby International survey conducted between March and September showed that nearly three times as many Nader backers prefer the Democrat to the president.

But evidence suggests that anti-Nader efforts have mitigated some of the potential that his candidacy will hurt Kerry. Frank Newport, editor in chief of the Gallup Poll, said his research has shown for months that when Nader is removed from poll questionnaires, the margin separating the two major candidates is unaltered.

Other studies indicate that Nader supporters are unlikely to support either major-party candidate. Pew's Keeter said the majority of the Nader voters he has tracked do not identify with either major political party. Richard Bennett of the New Hampshire-based American Research Group said: "Especially since the debates, where Kerry shored up his base, it does not appear that many of the remaining Nader voters would vote for either Bush or Kerry."

Scott Rasmussen, president of Rasmussen Reports, which offers political analysis to corporate clients, said Nader's supporters are further from the mainstream of the Democratic Party than they were in 2000. "In 2000, if you lined up the characteristics of Nader's supporters and Gore's supporters, they essentially looked the same, in terms of issues and ideology, with the exception being that the Nader people did not like Al Gore."

Democrats and other groups are publicly pressing ahead with their efforts to whittle away Nader's remaining support by claiming that a vote for Nader is akin to a vote for Bush. DNC Chairman Terence R. McAuliffe this week renewed his call for Nader to withdraw from the race, "so that George Bush doesn't get another four years to lead us down the wrong path."

An anti-Nader organization called the Democratic Action Team reinforced that message by running a new television ad this week in Wisconsin, Iowa and New Mexico. Its message: "Ralph, don't do this to us again." A separate print ad campaign against Nader also began this week in 11 swing states, focusing on alternative newspapers.

Democratic officials said that, between now and Nov. 2, they have no plans to send surrogates, such as former Vermont governor Howard Dean, to battleground states to appeal to Nader supporters. Still, one DNC official said, "we don't want to draw too much attention to his candidacy."

Finer reported from Boston.

Democrats blamed Ralph Nader for the outcome of the 2000 election.