London - U.K. polling stations opened Thursday in local elections set to heap more pressure on beleaguered Labour Prime Minister Keir Starmer and showcase the rise of hard-right and left-wing populists.Polls opened at 7 a.m. across Scotland, England and Wales in the ballot that is Starmer's biggest electoral test since his July 2024 general election landslide victory ended 14 years of Conservative rule.Opinion polls predict grim results for Labour, which could amplify calls for Starmer, 63, to resign or face a long-rumored party leadership challenge.