OTTAWA, Sept 6 (Reuters) - Canadian Liberal Prime Minister Justin Trudeau, trailing in opinion polls, attacked his main rival on Monday for waffling on gun control and vaccine mandates as the campaign enters its final stretch ahead of the Sept. 20 election. Conservative leader Erin O"Toole on Sunday scrapped a campaign promise to eliminate a ban on some assault weapons, a sensitive issue in Canada after mass shootings in recent years. Trudeau sought to capitalize on his opponent"s shift with just two weeks left to reverse his fortunes. O"Toole "will say anything to try and get elected," Trudeau told supporters at a campaign event in southern Ontario, Canada"s most-populous province. "That"s not leadership. That"s not integrity." After being criticized by O"Toole for calling the election two years early during a rising fourth wave of the COVID-19 pandemic, Trudeau assailed his rival"s opposition to vaccine mandates, including for his own candidates. Trudeau said O"Toole was pandering to anti-vaxxers just as he had to the gun lobby. Anti-vax hecklers have shouted abuse and even death threats at Trudeau throughout his campaign. "Erin O"Toole is at least taking some of his cues from (the anti-vax crowd)," Trudeau said. "Canadians are beginning to see that that"s the future being offered by Erin O"Toole, a future of wishy-washy, weak leadership where he doesn"t stand up for what he believes in, doesn"t tell Canadians what he actually believes," he said. Speaking in Ottawa, O"Toole refused to say how many of his candidates had not been inoculated. He has said those who are not vaccinated must be tested daily. "Our approach, with respect to vaccinations, is we try and encourage and inform and work with people, but we will respect their personal health decisions," O"Toole said. Liberal strategists have said the crucial period of the campaign starts after Labor Day, because Canadians have been more focused until now on their summer vacations than the election. There are two debates this week, one in French and one in English, the only occasions left in which all the candidates will face one another on national television ahead of the vote. A rolling Nanos Research survey of 1,200 people for CTV on Sunday put the Conservatives at 34.9%, with the Liberals at 33.4%, and the left-leaning New Democrats at 18.9%. A day earlier, Nanos had the Conservatives at 35.5% and the Liberals at 33%.