David Foster pounded away at the keys while his wife, Katharine McPhee Foster, swayed through their backyard like an unpolished bridesmaid at a wedding reception, belting out a timely rendition of Tina Turner’s “Simply the Best” rewritten for Spencer Pratt’s mayoral campaign: “better than Karen Bass… and Nithya Raman.” In footage posted to Instagram by One America News Network anchor Alicia Summers, Pratt is seen facing the audience as the Fosters performed on Monday night—representing a strangely poetic Hollywood moment for the candidate. Long before he was running for Mayor, “the Fos Man” (as Pratt refers to David Foster) encouraged the aspiring reality star to embrace his role as a villain—advice Pratt says helped turn him into one of the defining antagonists of 2000s television. During an appearance on the Joe Rogan Experience in April, Pratt recalled that Foster, who was previously married to Real Housewives of Beverly Hills star Yolanda Hadid, told him, “You got to be like Simon Cowell.” Years later, the Grammy-winning producer, whose daughters Erin and Sara Foster are behind the …