WASHINGTON (CNN)  -- In their first head-to-head debate, Sen. John McCain criticized Sen. Barack Obama as a candidate who "doesn't understand" the key issues the country faces, and Obama linked McCain to President Bush on several issues.



"I'm afraid Sen. Obama doesn't understand the difference between a tactic and a strategy," McCain said Friday as the two traded jabs over Iraq.



Obama shot back, "I absolutely understand the difference between tactics and strategy. And the strategic question that the president has to ask is not whether or not we are employing a particular approach in the country once we have made the decision to be there."



McCain drew from his experience overseas as he tried to portray himself as the more qualified candidate.



"Incredibly, incredibly Sen. Obama didn't go to Iraq for 900 days and never asked for a meeting with Gen. [David] Petraeus," he said.  Watch McCain, Obama talk about fighting in Iraq »



McCain slammed Obama for not supporting the surge, an increase of about 30,000 troops to Iraq in early 2007. Bush sent the additional troops as part of a campaign to pacify Baghdad and its surrounding provinces.



"John, you like to pretend like the war started in 2007," Obama shot back. "You talk about the surge. The war started in 2003, and at the time when the war started, you said it was going to be quick and easy. You said we knew where the weapons of mass destruction were. You were wrong." Watch entire debate:  Part 1 » |  Part 2 » |  Part 3 »



Obama repeatedly criticized the Bush administration and charged that McCain is an endorser of his policies.  See scenes from the debate »



In describing his tax plan, Obama said, "over time, that, I think, is going to be a better recipe for economic growth than the -- the policies of President Bush that John McCain wants to -- wants to follow."



Obama also said the economic crisis is the "final verdict on eight years of failed economic policies promoted by George Bush, supported by Sen. McCain."



Both candidates squeezed in a few cheap shots. Obama brought up McCain's jokingly singing a line about bombing Iran, and McCain jabbed Obama for his short-lived "presidential seal."



Immediately after the debate, both campaigns issued statements declaring their candidate the winner. Grade the candidates' performance in the debate



"This was a clear victory for Barack Obama on John McCain's home turf. Sen. McCain offered nothing but more of the same failed Bush policies, and Barack Obama made a forceful case for change in our economy and our foreign policy," said Obama-Biden campaign manager David Plouffe.



"John McCain needed a game-changer tonight, and by any measure, he didn't get it," he said. iReport.com: Who do you think won the debate?



McCain's campaign said "there was one man who was presidential tonight; that man was John McCain."



"There was another who was political; that was Barack Obama. John McCain won this debate and controlled the dialogue throughout, whether it was the economy, taxes, spending, Iraq or Iran. There was a leadership gap, a judgment gap and a boldness gap on display tonight, a fact Barack Obama acknowledged when he said John McCain was right at least five times," communications director Jill Hazelbaker said. Full coverage of the debates



During the first 30 minutes of the debate, the candidates focused on the economy, even though the debate was supposed to be centered on foreign policy.



For a while, it seemed like the debate might not even take place, because McCain said he would not show up unless Congress came to an agreement on the government's proposed $700 billion bailout plan.



McCain said Friday that enough progress has been made for him to attend the debate, even though Congress has not made a deal.



Here's a snapshot of what the candidates said.



On government spending:
What did the candidates debate? What did Obama say about McCain? Who accused Obama of failing to understand key issues? Who did McCain say doesn't understand? What did McCain say Obama doesn't understand? What did Obama say McCain was wrong about?
key issues "I absolutely understand the difference between tactics and strategy. And the strategic question that the president has to ask is not whether or not we are employing a particular approach in the country once we have made the decision to be there." Sen. John McCain Sen. Barack Obama the difference between a tactic and a strategy," You said we knew where the weapons of mass destruction were. You were wrong."
question: What did the candidates debate?, answer: key issues | question: What did Obama say about McCain?, answer: "I absolutely understand the difference between tactics and strategy. And the strategic question that the president has to ask is not whether or not we are employing a particular approach in the country once we have made the decision to be there." | question: Who accused Obama of failing to understand key issues?, answer: Sen. John McCain | question: Who did McCain say doesn't understand?, answer: Sen. Barack Obama | question: What did McCain say Obama doesn't understand?, answer: the difference between a tactic and a strategy," | question: What did Obama say McCain was wrong about?, answer: You said we knew where the weapons of mass destruction were. You were wrong."