WASHINGTON (CNN) - Ralph Nader announced Sunday he is entering the presidential race as an Independent.
In an interview with NBC's "Meet the Press," the consumer advocate said great changes in U.S. history have come "through little parties that never won any national election."
"Dissent is the mother of ascent," he said. "And in that context I've decided to run for president."
Nader, who turns 74 this week, complained of the "paralysis of the government," which he said is under the control of corporate executives and lobbyists.
It marks his fourth straight White House bid - fifth if his 1992 write-in campaign is included.
Nader's entry into the race did not come as a surprise to political watchers.
On Sunday, Sen. Barack Obama criticized him. "My sense is that Mr. Nader is somebody who, if you don't listen and adopt all of his policies, thinks you're not substantive," Obama told reporters when asked about Nader's possible candidacy.
- CNN's Josh Levs