WASHINGTON (CNN) -- Republican Rep. Ron Paul of Texas called on voters to back a third-party candidate for president Wednesday, rejecting his party's nominee and offering equally harsh words for the Democratic candidate.

Paul, who unsuccessfully sought the Republican presidential nomination this year, told supporters at the National Press Club in Washington that he is not endorsing GOP nominee Sen. John McCain or Democratic nominee Sen. Barack Obama.

Instead, Paul will give his seal of approval to four candidates: Green Party nominee Cynthia McKinney, Libertarian Party nominee Bob Barr, independent candidate Ralph Nader and Constitution Party candidate Chuck Baldwin.

Paul said he's supporting the third-party candidates because the two major parties and media had "colluded" to avoid discussing issues and falsely presenting the difference between McCain and Obama as real.

"I've come to the conclusion, after having spent many years in politics, is that our presidential elections turn out to be more of a charade than anything else, and I think that is true today. It is a charade," he said.

Paul offered an open endorsement to the four candidates because each signed onto a policy statement that calls for "balancing budgets, bring troops home, personal liberties and investigating the Federal Reserve," an aide to the congressman said.

Paul said a strong showing by the third-party candidates would express the public's frustration with the current system.

"I have no doubt that the majority is on our side," Paul added, citing public opinion polls. "We represent the majority of the American people."

Paul said that he had received a call from the McCain campaign Tuesday asking for his endorsement. Paul's response: "I don't like the idea of getting 2 to 3 million people [Paul supporters] angry at me."

McCain's aides argued that the Texas Republican should endorse McCain because he would do a "little less harm" than Obama, Paul said, but "we just don't need to do that anymore."

"If you ever get to the point where you believe the two parties are essentially the same, if the majority is outside of the establishment, it's not very democratic. The process is not working," Paul said.

Paul attacked Obama, saying, "He's not for change," and the congressman argued that his efforts would help the Republican Party.

"If the Republican side realized what I'm trying to do, they should be funding me," Paul said.

Paul failed in his bid for the Republican nomination, but he found a large, diverse audience for his anti-war and anti-tax messages.

The Texas congressman's campaign was fueled by an on-line, grass-roots fundraising operation. Throughout the campaign, Paul supporters called on others to join the "Ron Paul Revolution."

At the Republican National Convention last week in St. Paul, Minnesota, Paul supporters threw their own party in Minneapolis. iReport.com: See Ron Paul signs raised high at the "counter-convention"

Paul, who said he entered the presidential race reluctantly, told the roaring audience, "I lost my skepticism. I hope you lost your apathy."

"I did not want to run people's lives. I did not want to run the economy and I did not want to run the world. I didn't have the authority to do it, and I didn't have the Constitution behind me to do it," Paul said. Read more on Paul's rally

CNN's Mark Preston, Kristi Keck and Scott J. Anderson contributed to this report.

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