The Florida Supreme Court has ruled that maverick politician Ralph Nader can be on ballot papers in the November US presidential election.
Nader has already been struck off the ballot in four states
The decision is regarded as a blow to Democratic Party candidate John Kerry.
In the 2000 election Mr Nader attracted enough left-leaning voters in Florida - a key swing state - to cost the Democrats the presidency, analysts say.
The Democratic Party unsuccessfully argued that Mr Nader's Reform Party was not a genuine national organisation.
The Florida Supreme Court said it was not clear what constituted a national party, and that therefore it could not bar Mr Nader from running in the state.
Mr Nader was a candidate for the Green Party in 2000, when Mr Bush won Florida by 537 votes to clinch the presidency.
Most of Mr Nader's 98,000 votes would have gone to Democratic candidate Al Gore, had Mr Nader not been on the ballot, according to observers.
This year Mr Nader has been endorsed by the Reform Party - which first shot to prominence in 1992 with the candidacy of populist billionaire Ross Perot.
The Democrats argue that the party no longer has a nationwide following, and that it is supported by Mr Bush's camp in an effort to undermine Mr Kerry.
In an angry reaction to Friday's ruling, Democratic National Committee Chairman Terry McAuliffe said: "In state after state, Nader has become an extension of the Republican Party and their corporate backers."
The Reform Party has accused the Democrats of stifling democracy by trying to get their candidate struck off ballot papers.
"We are relieved with the Supreme Court ruling to enable our
candidate to be on the November ballot," said Patrick Slevin,
of the Reform Party in Florida.
"But we are also angry and disappointed we had to go through
this process to begin with. This is a black eye for Florida, and it
should have never have happened."
The Florida battle mirrors similar legal arguments across the United States.
The BBC's Michael Buchanan in Washington says the Democrats are particularly keen to avoid giving Ralph Nader ballot access in the most closely contested states.
The Florida decision means Mr Nader will compete in 20 southern states, while 15 are still considering his application.