SAN DIEGO -- Republican presidential candidate Ron Paul Friday encouraged about 400 of his supporters at the Community Concourse to remain active in politics even after his campaign comes to an end.

Paul, the lone GOP challenger to presumptive nominee John McCain, urged the people in the crowd in a 40-minute speech to continue their "meet ups" and remain involved for the next campaign.

"This campaign is nearing an end but the revolution has only begun," Paul said.

The congressman, who has a Libertarian-like theme of ending government intervention into private affairs and stopping U.S. foreign military entanglements, said he at first had no idea how many people would pick up on his message of liberty.

"There's many more than I ever dreamed of," Paul said. "This year has been fantastic. The numbers of people who've joined (the campaign) has been impressive. I'm more optimistic than I was a year ago."

Americans "are waking up" to the changes needed in their government, he said.

Paul has accumulated 30 GOP delegates during the primaries, a distant fourth behind Sen. McCain, R-Arizona, former Arkansas Gov. Mike Huckabee and ex-Massachusetts Gov. Mitt Romney, according to CNN.com. He's the only minor candidate in the party to have delegates, while two anticipated heavyweights, former New York City Mayor Rudy Giuliani and ex-Tennessee Sen. Fred Thompson won none.

He attracted a crowd to downtown San Diego that while mostly white, was diverse in age and culture. Young adults made up most of the audience, with more than a few children and senior citizens included. Some were in business suits, and others were punk-rockers with multi-colored hair and torn clothing.

"He's a champion of the constitution," said Patrick Keshishian, who traveled from Glendale to see Paul.

Keshishian said he caught a snippet of Paul in a Republican debate last November, and became hooked after conducting an Internet search about him.

Paul Wolf, a Navy petty officer, called Paul "a true conservative" for staying true to the constitution.

Wolf, of Ocean Beach, said he likes that the congressman wants to decrease spending on items that aren't necessary.

Paul told his audience that he was planning a rally next month in Texas, and another in Washington, D.C., in July. He said he hoped to follow up by taking a large contingent of supporters with him to the Republican National Convention in Minneapolis.