SAN FRANCISCO — Even the discovery fights in a federal challenge to Proposition 8 are weighty.

Gay marriage opponents trooped into Northern District Chief Judge Vaughn Walker’s courtroom Friday to quash requests for internal campaign e-mails and other documents from last year’s Yes on 8 effort. Marriage supporters, meanwhile, argued that the motivations of those behind the ballot initiative are highly relevant because discriminatory intent would undermine opponents’ claims of a rational state interest in the ban.