The U.S. President is never elected by popular vote. In fact, there have been four Presidential elections in U.S. history in which the winner of the election was not the candidate who received the most popular votes (in 1824, 1876, 1888 and 2000).
Incumbent President Franklin D. Roosevelt won reelection in the 1936 presidential election defeating Alfred Landon. In the 1936 presidential election Franklin Roosevelt received 523 electoral votes and Alfred Landon received 8 electoral votes. Incumbent President Ronald Reagan won reelection in the 1984 presidential election defeating Walter Mondale. In the 1984 election Ronald Reagan received 525 (97.58%) of the 538 electoral votes. Walter Mondale received 10 electoral votes from his home state of Minnesota and 3 electoral votes from the District of Columbia.
The election of Rutherford B. Hayes was the most contentious presidential election in US history. He was actually chosen by the US House of Representatives rather than by popular vote. No candidate received the required number of electoral votes.
In reference to the presidential election of 1876, Samuel J. Tilden won the majority of popular votes. However, he received one less Electoral vote than Rutherford Hayes, who went on to win the presidency.
Richard Nixon
Truman
Andrew Jackson For sure Pg 466 under "The History of Presidential Nomination"
The outcome of the 1796 presidential election was controversial because it resulted in the first contested election in American history. The Federalist candidate John Adams narrowly defeated the Democratic-Republican candidate Thomas Jefferson, but Adams's vice president was Jefferson's political rival, Thomas Pinckney. This created tension and a sense of political instability, as the president and vice president were from opposing parties.
In the 2000 presidential election, George W. Bush ran against Democratic candidate Al Gore. The election was one of the closest in U.S. history, culminating in a controversial Supreme Court decision that effectively awarded Florida's electoral votes to Bush, securing his presidency despite losing the popular vote.
1876... Hayes vs. Tilden
Presidential candidate James K. Polk was a pro-expansionist in the election. His opponent, Henry Clay, had no real position on it but had a history of respect for others' lands - being against Jackson's Indian Removal Act - so the clear choice to the people was Polk.
Harry Truman won the 1948 presidential election defeating Thomas Dewey. In the 1948 presidential election Harry Truman received 303 electoral votes and Thomas Dewey received 189 electoral votes. The popular vote totals were Truman 24,179,345 and Dewey 21,991,291. Truman's victory was one of the greatest election upsets in American history. Virtually every prediction indicated Dewey would defeat Truman.