NEW YORK - Forty-five years after Martin Luther King's dramatic call for racial equality in America, Barack Obama accepted the Democratic nomination to become the first African-American presidential candidate of a major political party. At a huge rally on Thursday night in Denver, Colorado, Obama offered his candidacy as an antidote to the "broken politics in Washington," and repeatedly drew contrasts with Republican John McCain, describing him as an extension of President George W. Bush and calling on the country to say: "Eight is enough." "America, we are better than these last eight years," said Obama , 47, a first-term Democratic senator from Illinois. "We are a better country than this." AFGHANISTAN Obama , who has vowed to use military force against al-Qaeda operatives in tribal areas if Pakistan doesn't act, pledged change, saying he would end the Iraq war and finish the fight against terrorists in Afghanistan. He promised tough diplomacy in dealing with Iran and Russia and build new partnerships to defeat threats of the 21st century as he faulted the Bush administration in the fight against terrorism and criticized Senator  McCain's position on Iraq war and counterterrorism. IRAN "I will end this war in Iraq responsibly, and finish the fight against al Qaeda and the Taliban in Afghanistan. I will rebuild our military to meet future conflicts. But I will also renew the tough, direct diplomacy that can prevent Iran from obtaining nuclear weapons and curb Russian aggression, referring to Moscow's intervention in Georgia. "I will build new partnerships to defeat the threats of the 21st century: terrorism and nuclear proliferation; poverty and genocide; climate change and disease. And I will restore our moral standing, so that America is once again that last, best hope for all who are called to the cause of freedom, who long for lives of peace, and who yearn for a better future." Obama spoke for 45 minutes before a 84000 crowd as the four-day Democratic National Convention sought to overcome any party divisions in the wake of a tense primary fight between the Illinois senator and former first lady Senator Hillary Clinton. In the resulting healing of the rift, Both former president Bill Clinton and Ms. Clinton pledged to support Obama . In his speech, Obama reacted sharply to the Republican criticism of his limited credentials in foreign policy and security areas and challenged his opponent Senator McCain's position on wars in Iraq and Afghanistan. "As Commander-in-Chief, I will never hesitate to defend this nation, but I will only send our troops into harm's way with a clear mission and a sacred commitment to give them the equipment they need in battle and the care and benefits they deserve when they come home," he said. IRAQ VOTE "For while Senator McCain was turning his sights to Iraq just days after 9/11, I stood up and opposed this war, knowing that it would distract us from the real threats we face. When John McCain said we could just 'muddle through' in Afghanistan, I argued for more resources and more troops to finish the fight against the terrorists who actually attacked us on 9/11, and made clear that we must take out Osama bin Laden and his lieutenants if we have them in our sights." "And today, as my call for a time frame to remove our troops from Iraq has been echoed by the Iraqi government and even the Bush Administration, even after we learned that Iraq has a $79 billion surplus while we're wallowing in deficits, John McCain stands alone in his stubborn refusal to end a misguided war." On Thursday, McCain acknowledged the historic importance of Obama 's nomination as the first African American presidential candidate, saying "Tomorrow, we'll be back at it. But tonight, Senator: Job well done." On Friday, McCain named a woman -- Governor Sarah Palin of Alaska -- as his running mate, who is not very well known here. Obama 's vice presidential running mate Senator Joseph Biden is a top foreign policy voice in Washington and has also been urging greater focus on Afghanistan. Obama mixed substance with storytelling, taunting McCain while laying out his own vision and biography. He went on the attack but also attempted to soften his edges, casting himself as an ordinary American who can identify with ordinary American families. He explicitly defended himself against Republican charges that he is merely a celebrity figure, although critics were quick to highlight how that message appeared at odds with the grandness of the evening - a stadium packed with 84,000 cheering admirers, a stage with Greek columns and a fireworks display. The speech marked the first outdoor acceptance speech by a presidential nominee since John F. Kennedy in 1960. Obama drew some of the strongest applause when he briefly invoked King - referring to him simply as a "young preacher from Georgia" - the slain civil rights leader who on this date 45 years ago delivered his moving "I Have a Dream" speech at the Lincoln Memorial. For a candidate who has often dazzled voters from the moment he sprang onto the national stage at the 2004 Democratic convention, Obama did not disappoint his audience. He packed the football stadium, from the field level to the top rafters, with supporters who wanted to win an election or simply witness history.