A quick note on the criteria I've used:
1) Because I am defining "reelection campaign" as an effort made by an incumbent to seek additional time in office, former presidents who sought new terms while not in power (i.e., Martin Van Buren in 1848, Millard Fillmore in 1856, Grover Cleveland in 1892, and Theodore Roosevelt in 1912) are not included.
2) Similarly, even though the term "reelection campaign" technically refers to someone who is seeking a political office after having already won it once before, this definition ignores those presidents who did not ascend to that position by having been elected (and thus were never "elected" to it in the first place) but who nevertheless were asking the voting public to extend their tenures when they sought election for the very first time (i.e., Theodore Roosevelt in 1904, Calvin Coolidge in 1924, Harry Truman in 1948, Lyndon Johnson in 1964, and Gerald Ford in 1976). Since these campaigns were, for all intents and purposes, actual reelection bids, they are being classified as such here.
3) Even though forty-three men have served as president, only twenty-four appear on this list because five ran for president at a time when popular vote wasn't counted (George Washington, John Adams, Thomas Jefferson, James Madison, and James Monroe), five died during their first term (William Harrison, Zachary Taylor, James Garfield, Warren Harding, and John Kennedy), five were unable to be nominated by a major party for a new term (John Tyler, Millard Fillmore, Franklin Pierce, Andrew Johnson, and Chester Arthur), three decided not to seek reelection (James Polk, James Buchanan, and Rutherford Hayes), and one hasn't had the opportunity yet (Barack Obama).
Now for the list of presidential reelection campaigns. They are presented in descending order of success, with the losing candidates placed in italics:
1. Lyndon Johnson (Democrat-1964) - 61.1%
22. Benjamin Harrison (Republican-1892) - 43.0%
Some interesting observations become apparent when this list is more closely analyzed:
1) On seventeen of the twenty-six times a president has sought reelection, he was successful, a figure that can be reduced to a ratio of roughly two-out-of-three.
2) Of the nine presidents who failed to get reelected, six (exactly two-out-of-three) were defeated due to a popular perception that the economy had deteriorated under their stewardship (Martin Van Buren, Benjamin Harrison, Herbert Hoover, Gerald Ford, Jimmy Carter, and George H. W. Bush). That said, their losses can't be solely attributed to this factor, since four presidents who presided over significant economic declines were able to get reelected in spite of them (Ulysses Grant, Richard Nixon, Ronald Reagan, and George W. Bush). What separated Grant, Nixon, Reagan, and Bush II from their less fortunate counterparts was that they knew how to draw the electorate's attention away from the economy (Grant and Nixon by stoking public fears that their opponent was an ideological radical, Reagan by benefiting from a temporary economic upsurge which concealed how conditions had still worsened since he took office, and Bush by capitalizing on the September 11th terrorist attacks).
3) Of the remaining three presidents, two (John Quincy Adams and William Taft) were defeated because their inherently unlikeable public personas made them vulnerable to attacks from more charismatic opponents (Adams lost to Andrew Jackson and Taft, though technically losing to the equally dull Woodrow Wilson, had much of his base siphoned off by the third party candidacy of the wildly popular Theodore Roosevelt).
4) The last defeated president, Grover Cleveland, has the dubious distinction of actually having won the popular vote in his reelection bid; his loss occurred because his opponent, Benjamin Harrison, happened to win the electoral votes of several key large states by extremely small margins.
What can our current president learn from this list?
The good news is that, unlike Adams and Taft, charisma is not an issue for Barack Obama. Unfortunately, dealing with a fledgling economy is very much a problem for him, which means that his best hope for winning in 2012 is to (a) have the Republicans nominate an alienating radical like Sarah Palin or Mike Huckabee, (b) engage in blatant fearmongering, or (c) have the economy experience a turnaround. Since the first possibility is beyond his control (although I personally think Huckabee is likely to be the candidate) and the second is extraordinarily unethical, Obama's best bet would be to aim for having (c) occur, and as such fight strenuously to cause an improvement in economic conditions.
One can only hope that he realizes this.