Kucinich, 61, faces four challengers in the March 4 congressional primary in his campaign for a seventh two-year term in the House.
Kucinich, speaking at a union hall, said he remained focused on ending the war in Iraq and ensuring jobs, health care, education and retirement security for all.
"I won't be president, but I can continue to fight for these important issues as the United States congressman representing the community that is first in my heart, Cleveland, Ohio," he told supporters, who chanted "Dennis, Dennis" as he took the podium.
"Today we are recommitting our energy to a government that works for all of us and is open to all of us. ... A government that stands for truth, for civil liberties and for a constitution," he said. "And it starts today in Cleveland, Ohio, in the heart of America."
Kucinich made an urgent appeal on his Web site this week for congressional campaign contributions as "the only candidate who can't be bought - 'cause he's not for sale."
He got only 1 percent of the vote in the New Hampshire presidential primary and was shut out in the Iowa caucuses.
Kucinich, a liberal former Cleveland mayor, lost a court battle with MSNBC over being excluded from a presidential debate in Nevada. He also fought with the Texas Democratic Party over a loyalty oath all candidates must sign to make the ballot.
Kucinich would not rule out another run for the presidency, but asked specifically if he would try again in 2012, he said, "that's the last thing on my mind."
