Massive Polish opposition rally ahead of pivotal election points to tight race

Donald Tusk leads large opposition rally of possibly up to one million people in Warsaw to galvanize supporters before October 15 parliamentary election.
Polls indicate tight contest between Tusk's pro-EU alliance and ruling conservative Law and Justice party led by Jaroslaw Kaczynski.
Opposition warns of Poland's potential exit from EU under current government and erosion of rights.
Ruling party campaigns on anti-immigrant platform and social spending pledges.
Election outcome could determine Poland's future relations with EU and stance on issues like tolerance and democracy.