"America is ready for change," Richardson told a cheering crowd at Invesco Field at Mile High on Thursday, the last day of the Democratic National Convention, "but (likely Republican challenger) John McCain has only changed his mind" on taxes, immigration and global warming.
"John McCain may pay hundred of dollars for his shoes, but we're the ones who will pay for his flip-flops," Richardson said.
Obama, the U.S.senator from Illinois, was declared the Democratic presidential candidate Wednesday by acclamation, becoming the first black major-party presidential candidate.
"We need a president who is first day in office says this, 'I will follow and uphold and respect the Constitution of the United States,' and then actually does," he said.
Richardson, who ran in the Democratic primary, said Americans can honor McCain's service to the United States, "but that doesn't mean we have to make him president."
Whipping the enthusiasm of the thousands at the stadium, Richardson concluded, "Are you ready to take our country back? Are we going to win this election? For America's future? Let's do it!"