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Presidents Day fact: Historians generally agree that Abraham Lincoln was the greatest U.S. president.

President Obama seems to agree, too. He announced his first run for president from the steps of the state house in Springfield, Ill., and laced it with references to No. 16. Asked during a "fireside hangout" on Google+ what people should read to really understand his political philosophy, Obama pointed first to his own book, then directed people to the writings of Lincoln.

"I have to tell you that where I draw inspiration from is the writings of Lincoln, and I'm assuming you're a Republican," he told a questioner. "This was our first Republican president. But the core philosophy that he espouses, this sense that we are this nation that is built on freedom and individual initiative and free enterprise but there are some things we do in common together," he said.

Obama caught some flak in December of 2011, during a "60 Minutes" interview, for comparing his own accomplishments to those of other presidents.

"I would put our legislative and foreign policy accomplishments in our first two years against any president - with the possible exceptions of Johnson, FDR and Lincoln - just in terms of what we've gotten done in modern history," Obama said.

It is surely too soon to say how great, or not, President Obama's presidency will be. But as he embarks on his second term, his legacy will be a topic of great debate and subject to political perspective.

John F. Kennedy told the presidential biographer David Donald that rating presidents was a tricky business.

"No one has a right to grade a president - even poor James Buchanan - who has not sat in his chair, examined the mail and information that came across his desk, and learned why he made his decisions," Donald wrote in his biography of Lincoln.

While "President's Day," which was enshrined as a Monday holiday with the " Uniform Holiday Bill" signed into law by Lyndon Johnson in 1968, is more closely pegged to Washington's Birthday, Richard Nixon appears to have started the tradition of referring to it as Presidents Day and honoring all the presidents, even though some surely deserve less commemoration than others. Good thing for him, too, because he's the only president to resign in the face of impeachment.

How a person views a president's legacy might have a lot to do with his or her political perspective. George Washington and Abraham Lincoln transcend those preferences; Washington helped create the country and Lincoln helped keep it intact and end the stain of slavery. But others - Woodrow Wilson, who is considered great - might be more well liked by a liberal than Ronald Reagan, who would surely be preferred by a conservative.

Somebody on Wikipedia took the time to compile surveys of scholars and the general public about who was the best president. Lincoln was rated highest the most. His predecessor, James Buchanan, is often cited as one of the worst because he allowed the Confederacy to fester. Another contender is Warren G. Harding, who followed Woodrow Wilson's international activism with a hands-off approach and a corrupt cabinet.

Newt Gingrich is a history professor and a politician and while his own presidential aspirations came up short in the Republican primary last year, he also has some bipartisan ideas about who were the best presidents: Washington or Lincoln, he said through a spokesman.

But he has often spoken up about the greatness of Democrat Franklin D. Roosevelt, the longest-serving president who grew the federal government more than any other. When Gingrich reached some heights of Washington power in 1995 as speaker of the House, the first Republican to hold the position in 40 years, he gave some cross-partisan love to FDR, the same president many Republicans now blame for bloating the federal government.

In a speech to the House of Representatives, he outlined the need for spending cuts to balance the budget, which he thought should exempt Social Security. But he said Washington should not be afraid of cuts elsewhere. And he invoked F.D.R. to make that point:

"But let me say about everything else, whether it is Medicare, or it is agricultural subsidies, or it is defense or anything that I think the greatest Democratic president of the 20th century, and in my judgment the greatest president of the 20th century, said it right. On March 4, 1933, he stood in braces as a man who had polio at a time when nobody who had that kind of disability could be anything in public life. He was president of the United States, and he stood in front of this Capitol on a rainy March day and he said, 'We have nothing to fear but fear itself.'"

Elsewhere in that speech, Gingrich gave praise to Franklin Roosevelt for the style of his leadership, not his policies.

"The fact is that it was Franklin Delano Roosevelt who gave hope to a nation that was in distress and could have slid into dictatorship. Every Republican has much to learn from studying what the Democrats did right," Gingrich told the House of Representatives in 1995.

Listen to Gingrich's 1995 speech here.

Gingrich's view of FDR's being the greatest 20 th century president has not changed in the intervening years. Asked during his presidential run who the fifth president n Mt. Rushmore should be, Gingrich said he'd "go for five and six: F.D.R. and Reagan."