WASHINGTON — The Supreme Court has frequently admonished judges not to interfere in election cases when the process is already underway, but it is now being accused of doing exactly that in recent decisions favoring Republicans in redistricting fights. The court’s ruling in a case from Louisiana that weakened the Voting Rights Act has set off a frenzy in some Republican-led states to draw new congressional maps that favor their party. The stakes are high ahead of this year’s midterm elections