Republican strategist Ed Rollins says he doubts efforts to take down the real estate tycoon will work. “Trump’s support is different,” says Rollins, a former Ronald Reagan official who advised Mike Huckabee in 2008 and Michele Bachmann in 2012. “They already have heard all the negatives and don’t care. … Trump is running as the anti-Washington candidate, and this just makes his case: ‘Washington and the Republican establishment don’t want me because I represent you, not them!’” 

Club for Growth spent $1 million on ads in Iowa pointing out Trump’s flip-flops over the years, apparently to no avail. The group would like to raise more money for the effort, according to the Wall Street Journal report.

Trump opponents even tried to bar him from competing in New Hampshire but failed. Former state party chairman Fergus Cullen’s formal efforts to have Trump removed from the ballot on the grounds that he’s not a true Republican were dismissed by the state ballot commission.

Trump opponents believe that even though the developer and reality TV star continues to lead in polls, voters are starting to pay closer attention to details as the election nears. And while other efforts to put down Trump have failed—and even backfired against some candidates who tried—opponents believe paid advertising against him and a more cohesive and concerted effort will make a difference this time.