Hundreds of thousands of people gathered in central Warsaw on Sunday at a rally organised by opposition leader Donald Tusk, two weeks before a crucial election that will have major implications for the future political course of Poland and its role in Europe. As a closely fought and vicious campaign enters its final straight, Tusk had called on supporters to put on a show of strength in Warsaw and galvanise the opposition. Victory, he claimed, was in sight. “A breakthrough moment is coming in the history of our homeland,” he said to the huge crowd at the beginning of the rally, his words echoing through surrounding streets from banks of speakers set up in several locations. “Let no one among the ruling team have any illusions. Change for the better is inevitable,” he added. Tusk claimed more than a million people had attended the march, dubbed the “March of a million hearts”, while Warsaw police claimed the number was about 100,000. The online news channel Onet.pl put the figure at between 600,000 and 800,000. Large parts of the centre of Warsaw came to a standstill as people streamed through the streets carrying Polish and European Union flags, as well as banners with various jokey or angry slogans attacking the ruling Law and Justice (PiS) party. “No one believed that such crowds and such emotions could happen again in our history. This is a sign of the great Polish revival,” said Tusk. Tusk was the Polish prime minister between 2007 and 2014 before leaving Poland to become president of the European Council. He has returned to Polish politics to lead the opposition campaign in what he has claimed is the last chance to save Polish democracy. PiS came to power in 2015 and has pursued a rightwing populist agenda combined with increased social spending, winning much support in rural areas. At the same time, the party has curtailed rights for women and minorities and been accused of democratic backsliding. Polls suggest PiS will do slightly better than Tusk’s Civic Coalition, and the final result is likely to come down to the performance of several smaller parties and the arithmetic around coalition building. PiS leaders held their own event in the city of Katowice on Sunday, timed to coincide with the Tusk march. They continued a campaign strategy of portraying the opposition leaders as foreign stooges, using Tusk’s years in Brussels to claim he now answers to German interests. “This vote is not only about what Poland will look like. It is about whether Poland will exist at all,” claimed the prime minister, Mateusz Morawiecki, brandishing a file he said contained damaging information about Tusk, who had a “German vision” for Poland’s future. A large part of Tusk’s campaign has been about reclaiming the language of patriotism for the opposition, leading to the red-and-white hearts that have become a symbol of the campaign. On Sunday, thousands in attendance at the rally were waving red-and-white Polish flags. “I see a sea of red and white banners … we all share the view that our red-and-white homeland can be home to free people again,” said Tusk. The years of PiS rule have seen a takeover of public media, increasing friction with Brussels and the introduction of some of Europe’s harshest anti-abortion laws. Rafał Trzaskowski, the Civic Coalition mayor of Warsaw, also addressed the rally, saying he hoped the elections would lead to a more “open and tolerant” Poland. “We are marching so that children do not have to watch their mothers being beaten because they are fighting for their rights … so that no one attacks kids with rainbow tote bags who are fighting for their rights,” said Trzaskowski. While the size of the rally will doubtless energise opposition forces as they enter the final stage of campaigning, most observers say the final outcome of the election is still impossible to predict with confidence. “It’s amazing to see so many happy, smiling people in one place and to get a sense of what a different place Poland could be,” said 41-year-old Joanna from Wrocław, who travelled to Warsaw with her two teenage daughters to attend the rally. “But I’m still really worried that PiS can win again, and then I will be worried for me, but especially worried for these two and their future in this country.”