Assassinations and assassination attempts, and threats, have affected American History, as is covered in my book, “Assassinations, Threats, And The American Presidency: From Andrew Jackson To Barack Obama”, Rowman Littlefield, August 2015.
But then there are cases, not covered in my book, of situations that could have occurred and affected American history, that have nothing to do with assassinations.
Witness the following:
In 1857, newly inaugurated President James Buchanan was extremely ill at the time of the inauguration, and almost failed to deliver his Inaugural Address, and was in bed for a few weeks after the inauguration, until he recovered. It was believed he might have been poisoned by an unsafe water supply at the hotel he stayed at before his inauguration. Had he died in office, Vice President John C. Breckinridge would have been President, and would have been only 36 years old, the youngest President in American history, and actually elected in November 1856, when he was still 35!
Stephen Douglas, Senator from Illinois, was the Democratic nominee for President in the Presidential Election of 1860, a four way race won by Abraham Lincoln, but had Douglas won, he would have died in office three months later, two months after the Civil War had begun, transforming the whole era if that had occurred!
In 1872, Democratic and Liberal Republican Presidential nominee Horace Greeley, who lost the Presidential Election of 1872 to President Ulysses S. Grant, died three weeks after the election, and before the Electoral College met. What if he had won the election? It would have meant that Vice Presidential nominee, B. Gratz Brown, Governor of Missouri and, earlier, Senator from Missouri, would have been President!
President Chester Alan Arthur (1881-1885) succeeded President James A. Garfield after his assassination in September 1881, and finished out the term, but was denied nomination for a full term in 1884, which turned out to be fortunate as Arthur died in 1886, and therefore, would have died in office!
President Grover Cleveland, in his second nonconsecutive term in the White House from 1893-1897, had serious surgery for cancer of the jaw in 1894, done in secret on a boat on the Hudson River, and kept secret until after his death in 1908. Had he died of cancer, Vice President Adlai Stevenson, the grandfather of Democratic Presidential nominee, Adlai Stevenson II in 1952 and 1956, would have been President!
President William Howard Taft (1909-1913) saw his Vice President, James Sherman, die in office in October 1912, shortly before the Presidential Election of 1912, which Taft lost, in the worst reelection defeat of any President in American history, winning only two states. But when the Electoral College met, the name of Columbia University President Nicholas Murray Butler was substituted to count the electoral votes. However, there was no provision for a replacement Vice President, so had Taft won, he would have had no Vice President for the entire term of 1913-1917!
President Woodrow Wilson (1913-1921) had a severe stroke in September 1919, and never fully recovered in his last year and a half in the White House, and his wife ran cabinet meetings in his absence, but had Wilson resigned or died, Vice President Thomas Marshall would have become President!
Franklin D. Roosevelt had Henry A. Wallace, his Secretary of Agriculture, as his third term Vice President from 1941-1945, and had he not been lobbied to replace the unpopular Wallace with Harry Truman for his fourth term run for the Presidency, it would have been Wallace who would have succeeded FDR in the Presidency after 82 days of the fourth term in 1945!
FDR’s Republican opponents in the Presidential Election of 1940 were businessman Wendell Willkie for President, and Oregon Senator Charles McNary for Vice President. Had they won the White House, the nation would have faced losing both of them in the last year of the term–McNary dying in February 1944, and Willkie in October 1944, an unprecedented situation to have had both the President and Vice President in the same term die in office! And this would have occurred during the height of the battle to win World War II, a very dangerous time for such an occurrence!
Harry Truman’s Vice President in his full term from 1949-1953 was Alben Barkley, who wished to run for President in 1952, but was pushed aside since he was already in his 70s, and it was felt it was not a good idea to have a President of that age come to office. It was fortunate that this happened, since Barkley died in April 1956, so would have died in office!
President Gerald Ford replaced Vice President Nelson Rockefeller as his running mate in the 1976 election for Senator Bob Dole, under pressure from conservative Republicans led by Ronald Reagan, and lost the Presidential Election of 1976 to Jimmy Carter. Had Ford kept Rockefeller on the ticket, some think he would have defeated Carter, and if that was so, then Ford would have lost his Vice President in office, as Rockefeller died in January 1979!