WASHINGTON (Reuters) -Conservative U.S. Supreme Court justices signaled their willingness on Wednesday during arguments in a case involving Louisiana electoral districts to undercut a key section of the Voting Rights Act, the landmark 1965 federal law enacted by Congress to prevent racial discrimination in voting. A group of Black voters has appealed a lower court's finding that a voting map that added a second Black-majority congressional district in Louisiana was guided too much by racial considerations in violation of the constitutional promise of equal protection under the law. Louisiana, where Black people make up roughly a third of the population, has six U.S. House of Representatives districts.