Who was the presidential candidate with the highest popular vote ever?

Barack Obama won 69,498,516 popular votes in 2008, the highest total ever, due in large part to the constantly increasing population.

James Monroe won 80.61% of the popular vote in 1820. (George Washington no doubt did even better in 1788 and 1792 but he did not opposition at all.)

In modern history, Lyndon Johnson won the highest percentage of popular votes , 61.6% in 1964.