Former United States secretary of state Colin Powell has endorsed Democratic presidential candidate Barack Obama for the White House.
Mr Powell, a Republican, served under President George Bush in his first term. The endorsement is seen as a serious blow to the Republican Party's candidate, John McCain.
The former head of the joint chiefs of staff also expressed disquiet at what he saw as a rightward shift that the Republican Party has taken under Mr McCain.
He also said Mr McCain's running mate, Sarah Palin, is not ready to be president.
Mr Powell said Mr Obama has shown that he is able to lead and inspire, and to reach out across America.
Mr McCain said he was not surprised at the decision and pointed to other former secretaries of state who have backed his candidacy, naming Henry Kissinger, James Baker, Lawrence Eagleburger and Alexander Haig - all Republicans.
Meanwhile, the Obama campaign announced it had raised a record $US150 million in September.
Mr McCain chose to accept public funding and is limited to spending $US84 million.
Mr McCain told supporters in Ohio on Monday that he will continue fighting to win the presidency despite his current lag in opinion polls.
Mr McCain, embracing his underdog position, warned that Mr Obama was a job-killing, free-spending socialist. He said Mr Obama had plans to "redistribute wealth" to the "more than 40% of Americans" who are too poor to pay income taxes.
But Mr Obama, addressing more than 10,000 supporters in Carolina, noted that mega-rich investor Warren Buffett had also endorsed him, adding that he was keeping odd company for a supposed raging left-winger.