9:48 pm MT: From Rick Klein, author of ABC's The Note: Sen. Barack Obama's convention speech offered twin challenges -- one to his opponent, one to the voters he wants on his side. And to all audiences listening, he showed he is ready for a fight. To Sen. John McCain, the message was stark: He will meet his challenges on McCain's own terms. On foreign policy, the economy, and most noticeably national security, Obama signaled a willingness to engage McCain, with a bite he hasn't shown in the past.To the country, his challenge was trickier: Accept this non-traditional candidate and channel your hopes into him. He offered a long list of policy proposals designed to appeal to the broad middle, and offered his own biography to answer the caricature being peddled by the McCain campaign."I don't know what kind of lives John McCain thinks that celebrities lead, but this has been mine," Obama said.This was not Obama's best speech, but neither was it supposed to be. Four years ago, he was introducing himself and sparked a movement; now, as he showed Thursday night, he's trying to win an election.His choice of tactics risks tarnishing an image; one Republican official monitoring the speech said he spent nearly 20 of his 44 minutes speaking on the attack.But perhaps that's the point: To Democrats who are sick of losing elections, there are worse things than rallying behind a fighter. And to a country that wants a change in direction, Obama offered himself up as -- yes -- a hope.Check back tomorrow for more in tomorrow's Note.