Early in 1967, Spencer began having an affair with Grace Slick, herself a newcomer to the band [Jefferson Airplane]. They formed a faction, and exerted tremendous influence once the group became famous. According to most accounts, Spencer bullied the others into getting his way by routinely threatening to quit. Grace, at least tacitly, went along with him; as neither was yet signed to the band or RCA, the possibility of Grace going solo was very real.
Spencer is often cited as the culprit behind the sacking of Bill Graham as acting manager in early 1968. Graham wanted the Airplane to work harder and make more money, but the band members were fed up with the schedule he demanded of them. Spencer, with Grace`s approval, gave the band an ultimatum: either Graham went or they did.
Spencer`s heavy drinking and questionable judgment were often the source of strife within the band. For a time, he and Grace shared an apartment next door to Jorma and Margareta Kaukonen, but the place was burned to the ground when Spencer left groupies in charge of it. Spencer would openly pick up other women in front of Grace and later took to carrying a gun. He was also constantly complaining about matters; in one interview, he estimated that he had threatened to quit 28 times.
The final straw apparently came at Altamont. The Airplane performed at the Rolling Stones` free concert on December 6, 1969, the day after playing a concert in Florida. Mentally and physically exhausted, Spencer initially refused to play -- he said that the "vibes" at Altamont were wrong. (Ironically, he turned out the be right, as the free concert degenerated into violence and murder.) The others finally convinced him to play -- no one wanted to let down the people who had put the concert together -- but Spencer`s constant complaining almost provoked the band to violence.
By this point, Spencer`s relationship with Grace was all but over. On January 26, 1970, he married Sally Mann, a groupie, at the Airplane House with Grace as matron of honor.