Democrats could be participating in a "mini-Watergate" effort to get Ralph Nader (search) out of the presidential picture, the consumer advocate charged Thursday.

"They're hiring lawyers to go up to technicalities in places like Arizona, they infiltrated our political convention," Nader, an independent candidate for president, told FOX News on Thursday. "I spoke to John Kerry and said 'you'd better look into it because it could be a mini-Watergate, possibly."

Nader said he hasn't yet heard back from the Democratic senator from Massachusetts, who is hoping to oust President Bush from the White House in the November elections.

"This is pretty serious, when you try to lock the civil liberties of American just to get on the ballot so people can vote for the candidate of their choice," Nader continued.

Nader was denied a spot on the Arizona ballot and last Friday again accused the Democrats and Kerry of engaging in political "dirty tricks."

Just hours before the developments in Arizona, Nader complained that the Democratic Party has "stepped up its obstruction tendencies" in challenging his ballot access. The consumer advocate said he had called the Kerry campaign three times last Thursday, asking to chat with the candidate.

"We have to get a clarification if they're going to engage in dirty tricks," Nader told reporters at a news conference to criticize multinational corporations.

The Kerry campaign dismissed Nader's complaints, arguing that Democrats were following the rules when they legally challenged Nader's signatures to get on the ballot. "These are rules that have been on the books for years and they ought to be followed," said Chad Clanton, who added that the Massachusetts senator would be happy to talk to Nader.

In Arizona, supporters of Nader abandoned their effort to get the independent candidate on the presidential ballot after Democrats challenged the validity of thousands of signatures.

Nader's campaign had submitted more than 22,000 signatures to Arizona election officials June 9 -- far more than the 14,694 valid signatures required by state law to compete against President Bush and Kerry.

"They really erect all kinds of barriers blocking voices and choices," Nader told FOX News of such alleged Democratic acts.

Although he's no fan of Republicans, the GOP "don't whine and carp like the Democrats," Nader said, adding that 10 times more Democrats "deserted the party" and voted for Bush in 2000 than voted for him.

When asked if Republicans are working behind the scenes to get him on the ballot, Nader said he doesn't know much about that but "we've seen lots of examples of Democrats trying to obstruct us … this is a fight for all third parties and independent candidates."

And with a reported 42 percent of Americans wanting troops to return from Iraq; over half of whom think it was mistake to send them there, Nader said, "there's no candidacy except the Nader-Camejo ticket speaking for them," adding that he provides the only anti-war platform for voters this year.

Nader is scheduled to debate former Vermont Gov. Howard Dean in Washington on Friday. Dean was the front-runner in the Democratic primaries until his campaign seemed to internally combust; he later dropped out of the race.

"Dean really made his mark by being against the war now he's back into the fold so we'll have fun tomorrow," Nader said.

Nader told reporters last week that he expects to get on about as many state ballots as he did in 2000 when his name was listed in 43 states and the District of Columbia. So far, he has not gotten on any ballot independently.

Many Democrats blame Nader, the Green Party (search) candidate four years ago, for taking votes from Democrat Al Gore and helping ensure President Bush's election. He has been endorsed by the Reform Party (search), which has ballot lines in at least seven states.

Fox News' Liza Porteus and The Associated Press contributed to this report.