More despicable campaigns - via here
1876: Rutherford Hayes vs. Samuel Tilden -- This is the granddaddy of them all: a truly stolen election in which Republicans turned defeat into victory for Rutherford Hayes by counting Democratic votes as their own in three Southern states. Both parties used violence to intimidate former black slaves for their votes. And not to mention that Republicans extorted 2% of the salaries of Federal employees to aid in their campaign efforts, or that Democrats accused Hayes of shooting his mother and robbing the dead, or that Republicans claimed that Samuel Tilden suffered from venereal disease.
1964: Lyndon Johnson vs. Barry Goldwater -- Not as well know as Nixon's 1972 dirty tricks election, Johnson's 1964 win over Goldwater featured the cynical manufacturing of anti-Goldwater stories planted with gullible reporters; children's coloring books portraying Goldwater as a Klansman; CIA invasion of Goldwater's campaign; and FBI bugging of Goldwater's campaign plane.
1800: Thomas Jefferson vs. John Adams -- Way back in only the third election ever held in this country, Thomas Jefferson of the Republicans and John Adams of the Federalists went at it tooth and nail, with Republicans hiring hack writers to attack the incumbent Adams as a "hideous hermaphroditical character." whatever that means, and Federalsts claiming that Jefferson slept with slaves. Thomas Jefferson claimed incumbent John Adams wanted to marry off his son to the daughter of King George III, creating an American dynasty under British rule. Jefferson haters called the challenger a fraud, a coward, a thief, and "a mean-spirited, low-lived fellow, the son of a half-breed Indian squaw, sired by a Virginia mulatto father." The close election was thrown into the House of Representatives, where Jefferson almost certainly made a secret deal to win it all.