That burden is prompting civil rights and voting groups to recalibrate their approach to challenging in court the raft of new restrictions that Republican-controlled legislatures have passed this year in the aftermath of Donald J. Trump’s election loss in November. No longer, they say, can they count on the federal courts, including the Supreme Court, to serve as a backstop for preventing racially discriminatory voting restrictions. “We have to remember that the Supreme Court is not going to save us — it’s not going to protect our democracy in these moments when it is most necessary that it does so,” Sam Spital, the director of litigation at the NAACP Legal Defense Fund, said Friday... The court did not address the purpose clause of Section 2. But those cases often rely on racist statements by lawmakers or irregularities in the legislative process — trickier elements of a legal case to prove than the effects. “You’re not going to get that smoking gun kind of evidence,” said Sophia Lakin, the deputy director of the A.C.L.U.’s Voting Rights Project. “It’s pulling together a lot of circumstantial pieces to show the purpose is to take away the rights of voters of color.”