In a rousing speech that has become the hallmark of his march from obscurity to the Democratic Presidential nomination, Sen. Barack Obama of Illinois accepted the challenge of becoming his party’s presumptive nominee and detailed the change that he has promised to bring to the political process.

It was a historic moment in American politics and the nation’s history and even Hillary Rodham Clinton’s refusal to be gracious and admit defeat could not destroy the significance of the evening.

Watch the MSNBC video of his speech: