Hubert Humphrey had been a popular president up to this point but had drawn criticism from political opponents on both the left and right.
He drew criticism from southern democrats for signing the bipartisan Civil Rights Act of 1969 into law on July 10th of that year, which was noted for causing violent protest in the south. On July 16th, in Selma, Alabama, just 6 days after the signing of the act, Martin Luther King Jr. was giving a speech congratulating President Humphrey when all of a sudden, an armed segregationist shot King in the back, fatally wounding him, and he would die in the hospital early the next morning at the age of 40. Humphrey would later give a eulogy at King's funeral. He also drew some criticism from other right wing democrats for apparently being too soft on counterculture protests as well, most notably from California Governor Sam Yorty, who would prove to be one of Humphreys most outspoken democratic critics. Humphrey's middle-line stance on the counterculture protests angered progressives in the party too.
Despite his high approval numbers, Humphrey was challenged by 3 big name politicians in the democratic primary, Governor George Wallace of Alabama, former Senator Eugene McCarthy of Minnesota, and most notably, Sam Yorty. However Humphrey still held the establishment backing, and through the endorsement of Bill Daley, Humphrey was able to sail through the primaries and into renomination with little issue, winning every single primary contest. However, Humphrey and Vice President Connally had rifts of their own, and the latter ultimately refused to run alongside Humphrey again. He would unsuccessfully attempt to negotiate to grab the VP nomination for the Republican party after switching his registration, but placed a close 2nd at the convention.
The Republicans had been attempting to distance themselves from the flop that most historians of the time described the Goldwater presidency as being as much as they could following their landslide defeat in 1968. Despite this, the conservative faction was still a very strong percentage of the party demographic. The undoubted successor to Goldwater's conservative faction was freshman senator Evan Mecham, who had won the senate seat opposite to the one Goldwater himself held. The candidate the moderates would put up was less certain, 2 moderate faction big-wigs, Nelson Rockefeller and George Romney, ran for the nomination. This along with 3 favorite son candidates syphoning off even more of the moderate vote, the moderate vote split almost resulted in Mecham winning the nomination, but Romney and favorite son Charles Percy combined their delegates with Rockefeller's delegates, giving him a majority on the 2nd ballot.
Mecham and the conservatives decried this, calling it a second corrupt bargain. 316 conservative delegates walked out of the convention and Mecham would announce a 3rd party bid under the American Independent Party. The previous nominee, John G. Schmitz would withdraw the nomination in exchange for the VP slot.
Humphrey played his reelection campaign safe, rarely making many campaign attacks against either Rockefeller or Mecham. Rockefeller played the same strategy. Mecham heavily attacked both Humphrey and Rockefeller, but ultimately attacked Rockefeller more than Humphrey, which did aid in siphoning off votes from Rockefeller.
The election was always close, as the financing juggernauts of Rockefeller and Humphrey filled the airwaves with ads. Mecham didn't have that much room to compete, but Mecham had been able to partially replicate the folksy populist draw of George Wallace's 1968 campaign, and received loads of support in the south.
Rockefeller was hoping that Mecham would work towards siphoning southern democrats off of Humphrey and cause a wide enough split to allow him to win. Mecham hoped he would be able to deadlock the election. But they turned out to both have overestimated their abilities, as the happy warrior marched on to a second term.
