Representative Ron Paul, the libertarian-leaning congressman from Texas who attracted a devoted following in his bid for the Republican nomination, is once again trying to shake up the presidential race.

At a press conference in Washington, D.C. on Wednesday, Mr. Paul plans to urge voters to support one of the third-party candidates for president rather than cast their ballot for either Senator Barack Obama, the Democratic nominee, or Senator John McCain, the Republican candidate.

“At a time when 60 percent of the American people are dissatisfied with their presidential choices,” Mr. Paul said in a statement, “this could be the year that third-party option brings in a big chunk of the vote.”



And Mr. Paul intends to showcase some of those options at the National Press Club on Wednesday. He will be joined by Ralph Nader, an independent candidate, Chuck Baldwin of the Constitution Party, former Representative Bob Barr of Georgia, who is running on the Libertarian Party ticket and former Georgia congresswoman, Cynthia McKinney, who is the Green Party’s presidential candidate.

According to a spokesman, Mr. Paul plans to say that the Republican and Democratic candidates “have no substantive differences on important issues.”

The four third-party candidates, on the other hand, have agreed to sign on to a four-point plan that includes balancing the federal budget, bringing American troops home, protecting civil liberties and investigating the Federal Reserve.

Mr. Paul’s iconoclastic ways have earned him the scorn of some, especially in the Republican party, who fear he could sap votes from Senator McCain on Election Day, even as he has continued to inspire others who back his reform agenda. Several thousand turned out for his “Rally for Liberty,” in Minneapolis last week, an alternative to the much Republican convention taking place nearby.

Despite that following, he has refused to run on an alternate ticket, saying he is a Republican.