He also noted that he'll appear on ballots alongside President Obama and Mitt Romney in all 50 states in November.
"Lots of opportunity to change the world a little bit," he said, describing his campaign. "I have seen nothing but increased crowds, increased appetite for what I have to say."
"A libertarian candidate's going to come at Obama from the left and come at Romney at the right," he predicted. Johnson, cautiously optimistic about his chances as a third-party spoiler in November, said more people are willing to consider voting for a third party in 2012 than ever before.
"There are more libertarians, people who declare themselves libertarian, than vote for a libertarian candidate," he said.
Johnson, the former Republican governor of New Mexico, dropped his bid for the Republican presidential nomination late last year in favor of running as a libertarian. He became the official third-party nominee in May and became eligible for federal matching funds last week.
But Johnson also credited Rep. Ron Paul (R-Texas) for standing for libertarian principles as a GOP presidential candidate. He endorsed Paul's bid for the presidency in 2008 and backed him for 2012 GOP Iowa caucuses shortly after dropping his own GOP bid.
"I'm delivering a message of liberty and freedom very much along the same lines as Ron Paul," he said. "I don't think Ron Paul's going to be successful winning the [Republican] nomination. I wish him luck. So that message goes away when his candidacy comes to an end."
Paul stopped competing in the primaries in mid-May, although he has not officially suspended his campaign. Romney has won enough delegates to cinch the nomination.