WASHINGTON — Many undecided voters have a common concern when they size up Barack Obama: his inexperience.
"I have nothing against Obama. I just think John McCain has more experience," said Steve Viernacki, an Ashley, Pa., restaurant owner.
Experts say that such worries are overblown.
"Experience matters, but its importance is terribly overstated," said historian Robert Dallek, the author of recent books about Presidents Kennedy, Johnson and Nixon.
Presidents with sterling resumes often have turned out to be busts, usually because they lacked the key quality a good president needs: sound judgment.
"John Quincy Adams understood the world, but he didn't have a political gene in his makeup," Richard Norton Smith, a presidential scholar at George Mason University, in Fairfax, Va., said of the nation's sixth president, who isn't remembered as successful.
Yet presidents with far lesser credentials have triumphed. John F. Kennedy was 43 years old when he took office in 1961, four years younger than Obama. Kennedy's early years were rocky, Dallek said, but "he was a quick learner" and his third and final year as president was masterful.
Obama, the presumptive Democratic nominee, has been a U.S. senator for three and a half years, but since the 110th Congress began in January 2007, he's missed about 45 percent of all votes while running for president. He's never chaired a major committee.
McCain, 71, the presumptive Republican nominee, was a member of the House of Representatives from 1983 to 1987, and has been a senator ever since. He's chaired Senate committees and authored several major bills, notably the 2002 campaign-finance overhaul.
Experts agreed that none of these experiences — or a lack of them — is an accurate predictor of either man's likely White House performance.
"The presidency has too many moving pieces. Trying to gauge whether experience matters really eludes measurement," said Carl Pinkele, a presidential expert at Ohio Wesleyan University, in Delaware, Ohio.
Scholars suggest two yardsticks — executive background and foreign policy expertise — but they also find both flawed.
Herbert Hoover was the widely admired U.S. food administrator in World War I, presidential adviser at the Versailles Conference and secretary of commerce in the 1920s.
"Yet his management of the economy was a disaster," Dallek said of Hoover's one-term presidency, which began months before the Great Depression.
Jimmy Carter also brought a management background, taking office in 1977 after one term as the governor of Georgia and more than 20 years running his family business. But "he was then universally criticized for being a micromanager in the White House," said John Baick, an associate professor of history at Western New England College, in Springfield, Mass.
President Bush has a master of business administration degree from Harvard University, served nearly two terms as the governor of Texas and surrounded himself in the White House with experienced advisers. But after seven and a half years in power he holds a dismal public-approval rating rooted largely in the Iraq war and the staggering economy.
Foreign policy also has proved to be an unreliable barometer.
Two presidents regarded as among the nation's weakest — John Quincy Adams and James Buchanan — had extensive diplomatic resumes. Adams held several diplomatic posts, was the secretary of state under President James Monroe and negotiated an end to the War of 1812. But he met difficulty when he tried to improve the economy with a road- and canal-building program and high tariffs, and he was trounced when he sought re-election in 1828.
Buchanan, who served as James Polk's secretary of state in the 1840s, spent the three years before his 1856 election as minister to Great Britain.
Yet "he's quite possibly the worst president in American history, because of his inability to effectively manage Southern secession and the slavery issue," said Chris Dolan, a professor of political science at Lebanon Valley College, in Annville, Pa.
Similarly, Bush's father had been the U.S. envoy to China, United Nations ambassador, the director of the Central Intelligence Agency and vice president for eight years.
But he was seen as an ineffective manager of the nation's economy, and the nation spurned his 1992 re-election bid, giving him the lowest popular-vote total of any incumbent president in 80 years.
What matters more than experience, scholars said, is an ability to hone and trust one's instincts.
"Give me good judgment every time," Dallek said.
Thomas De Luca, a professor of political science at Fordham University, in New York, cited Ronald Reagan as an example.
"Ronald Reagan had no foreign policy experience, but according to Republicans he was one of the most successful foreign-policy presidents ever," De Luca said.
Abraham Lincoln, whom most scholarly surveys rate as the nation's greatest president, had no training to be the commander in chief and almost no Washington experience. He served eight years in the Illinois legislature and two in the U.S. House of Representatives, and had been out of office for nearly 12 years before he won the presidency in 1860 with 39.9 percent of the vote.
South Carolina seceded from the union the month after he was elected. Yet Lincoln is highly regarded not only for keeping the union together through the Civil War, but for "a number of things in his administration that had nothing to do with the war," presidential historian Alvin Felzenberg said. Among them: authorization for building the transcontinental railroad and spurring the growth of public colleges.
Dallek and Smith pointed to Kennedy as a key modern example of a president who came to trust his judgment.
The young president made a series of highly public missteps in his early years in power, notably the April 1961 Bay of Pigs invasion and the May 1961 summit with Soviet Premier Nikita Khrushchev, who found Kennedy weak. The Berlin Wall went up three months later, followed by the Soviet effort to build missile bases in Cuba.
Kennedy would rebound, starting with his deft handling of the Cuban missile crisis in October 1962, which defused the most dangerous moment of the Cold War.
Smith also pointed to a two-day period in June 1963 as a key turning point. On June 10, Kennedy announced new talks on a nuclear test-ban treaty and called for an end to the Cold War. He'd sign the ratified pact in October.
On June 11, Kennedy faced a different test, when Alabama Gov. George Wallace stood at the door of the University of Alabama's administration building, barring two black students from registering.
Kennedy federalized the state's National Guard, the students registered and he went on national television to announce that he'd back strong civil rights legislation. That measure became the landmark Civil Rights Act of 1964, enacted after his assassination.
Kennedy's actions those June days were "the moments he mastered the presidency," Smith said. "He understood then how you take risks and use your political judgment."
Voters, though, don't go to history books to seek guidance on such matters. They go with their guts, and right now, many of them lament Obama's lack of experience.
Joe Lipinski, 82, a carpenter in Mocanaqua, Pa., vividly remembers Kennedy, and for him Obama doesn't compare. "I'm still a Democrat, but I just can't like Obama at this point," he said.
Call it lack of experience, said Theresa Mulaski, a Pittston, Pa., retiree, or call it a question about judgment, but it all comes down to this, she said: "I can't seem to get a grasp on Obama."