SPRINGFIELD, Ill. (AP) — Illinois voters have approved an amendment to their state constitution guaranteeing the right to bargain collectively. The measure in last week's election was closely watched in Illinois and beyond as a gauge of public support for the labor movement, which has lost ground for years in conservative-led states. Unions groups say it could signal a new chapter in the struggle over workers’ rights as U.S. union ranks have grown as everyone from coffee shop baristas to warehouse workers seeks to organize.