Pundits have lately been comparing Barack Obama to Jimmy Carter, suggesting he is a likely loser in 2012. But my American Enterprise Institute colleague Norman Ornstein, writing in the New Republic, compares Obama to Harry Truman, suggesting he might outperform the polls and win.

It's always helpful to be reminded that early polls may not be predictive and that opinion can change, as was the case when Truman won in 1948 and when Carter lost in 1980. But we should keep in mind that today's polls are better and more frequent than they were 63 years ago.

Gallup's last 1948 poll was taken between Oct. 15 and 25 and showed Thomas Dewey leading Truman by only 5 points. No contemporary pollster would quit eight days before the election after getting that result.

There are in fact major differences between Truman's standing in 1947-48 and Obama's standing today. Contrary to Truman's "do-nothing" characterization of the Republican 80th Congress, it in fact did a lot. It repealed wartime wage and price controls, cut taxes deeply and passed the Taft-Hartley Act limiting the powers of labor unions.

None of those actions was reversed by the Democratic Congress elected with Truman in 1948. Many congressional Democrats in those days were anti-New Deal conservatives. Truman won many votes from Democrats still upset about the Civil War. Few such votes are available to Obama or congressional Democrats in 2012.

In addition, Truman's victory was due to two "F factors"--the farm vote and foreign policy--the first of which scarcely exists today and the second of which seems unlikely to benefit Obama in the same way.

When the nation went to war in the 1940s one out of four Americans still lived on farms. The 1948 electorate still reflected that America. Voter turnout was actually lower than it was in 1940, and the vast postwar demographic changes were not reflected in elections until turnout surged in the contest between Dwight Eisenhower and Adlai Stevenson in 1952.

"...Truman's victory was due to two "F factors"--the farm vote and foreign policy..." -- Michael Barone

Truman promised to keep Depression-era farm subsidies in place and charged that Dewey and the Republicans would repeal them. That enabled him to run ahead of Franklin Roosevelt's 1944 showing in 13 states with large farm populations from Indiana to Colorado and Minnesota to Oklahoma.

Without that swing in the farm vote Truman would not have won. Dewey, waking up to find that he would not be president as he and almost everyone expected, spotted that immediately the morning after the election.

Today only 2 to 3 percent of Americans live on farms. Farm prices are currently running far ahead of subsidy prices. Obama is not going to be re-elected by the farm vote.

The second F factor that helped Truman was foreign policy. As Ornstein correctly notes, Truman's Cold War policies--the Truman Doctrine, the Marshall Plan--were supported by Republican congressional leaders and by Dewey. Top Dewey advisers were taken into confidence by Truman's foreign policy appointees. It was the golden era of bipartisan foreign policy.

But on one policy Truman went further than his top advisers or Dewey's. When the Soviets blocked land access to West Berlin in June 1948, Truman's advisers--men of the caliber of George Marshall and Omar Bradley--said that it was impossible to supply food and fuel to Berlin and we should just abandon it.

At a crucial meeting in July 1948 Truman listened to this advice. After others finished talking, Truman said simply, "We're not leaving Berlin." Gen. Lucius Clay, our proconsul in Germany, set about organizing what became the Berlin airlift.

Gen. William Tunner, who had run the wartime airlift from Burma to China, made the Berlin airlift work. Vast quantities of food and coal--far more than experts had estimated--were brought into Tempelhof Airport on planes landing in foul weather every 90 seconds. The pilots took to throwing out pieces of candy to the hungry kids lining the runways.

Andrei Cherny, now chairman of the Arizona Democratic Party, tells the story in his book "The Candy Bombers." He argues persuasively that the Berlin airlift--an example of American strength, determination, technological prowess and generosity--played a key role in re-electing Truman.

Truman's tough stand against communist aggression played a key part in his upset victory in 1948. Will Barack Obama have a similar accomplishment? Or will he be seen as impotent against our enemies, as was Jimmy Carter?

Michael Barone is a resident fellow at AEI.