WASHINGTON -- Barack Obama might want to think twice before accepting his party's nomination at the Democratic National Convention in Charlotte, N.C. Should he win re-election, the thrill of victory could give way the "Second-Term Jinx."

For more than a century, presidents have run into unforeseen woes in their second terms.

Some have been tragic. Abraham Lincoln and William McKinley were assassinated; Woodrow Wilson suffered a debilitating stroke. More have been political, scandals and controversies that set back their agendas or worse, tarnished their very place in history....