OXFORD, Miss.—John McCain accused Barack Obama of compiling “the most liberal voting record in the United States Senate” Friday night in their first debate of a close campaign for the White House. The Democrat shot back, “Mostly that’s just me opposing George Bush’s wrong-headed policies.”

Obama said his Republican rival has been a loyal supporter of the unpopular president across the past eight years, adding that the current economic crisis is “a final verdict on eight years of failed economic policies promoted by President Bush and supported by Sen. McCain.”

The two men clashed over spending, taxes, energy and—at length—the war in Iraq during their 90-minute debate.

McCain accused his younger rival of an “incredible thing of voting to cut off funds for troops in Iraq and Afghanistan,” a reference to legislation that cleared the Senate more than a year ago.

Obama disputed that, saying he had opposed funding in a bill that presented a “blank check” to the Pentagon while McCain had opposed money in legislation that included a timetable for troop withdrawal.

Obama opposed the invasion of Iraq in 2002, before he was a member of Congress, while voted to authorize the war as a member of the Senate.

“You were wrong” on Iraq, Obama repeated three times in succession. “John, you like to pretend the war began in 2007.”

McCain replied that Obama has refused to acknowledge the success of the troop buildup in Iraq that McCain recommended and Bush announced more than a year ago.

The two presidential candidates stood behind identical wooden lecterns on stage at the performing arts center at the University of Mississippi for the first of three scheduled debates with less than six weeks remaining until Election Day. The two vice presidential candidates will meet next week for their only debate.

The 47-year-old Obama is seeking to become the nation’s first black president. McCain, 72, is hoping to become the oldest first-term chief executive in history — and he made a few jokes at his own expense.

“I’ve been around a while,” he said at one point. “Were you afraid I couldn’t hear you?” he said at another after Obama repeated a comment.

It was a debate that almost didn’t happen. McCain decided at the last minute to attend, two days after announcing he would try to have the event rescheduled if Congress had not reached an agreement on an economic bailout to deal with the crisis now gripping Wall Street.

The two men were pointed but polite as they covered most issues, although at least once, McCain sought to depict his rival as naive on foreign policy. That was particularly true when it came to Obama’s statement that it might become necessary to send U.S. troops across the Pakistani border to pursue terrorists.

“You don’t say that out loud,” retorted McCain. “If you have to do things, you do things.”

McCain also seemed eager to demonstrate his knowledge of foreign policy, recalling the names of three former leaders of the Soviet Union in one sentence.