Roosevelt actually had served only seven-and-a-half years as president. Elected vice president in 1900, he was elevated to the White House in September 1901, when William McKinley was assassinated. Roosevelt served out the remaining three-and-a-half years of McKinley's second term, then was elected in his own right in 1904. Deferring to the two-term tradition, he declined to run again in 1908. But this was many decades before the Constitution was amended to limit presidents to two terms, so Roosevelt was free to change his mind and run again as often as he wished.