When asked by a questioner at a town hall meeting in New Hampshire, the candidate who was once viewed as a natural frontrunner said that he’d support whatever candidate wins the nomination. “I’ve been supporting Republicans since Richard Nixon,” he said, according to Reuters.

Bush also called Trump a “jerk,” continuing his campaign to convince voters that the top-polling candidate is unfit to be president. He said that Trump proved himself to be a poor presidential candidate when he appeared to mock the disability of a New York Times reporter, as well as when he fumbled an answer in a December debate about basic principles of U.S. nuclear defense policy. “I think when you’re asked about the nuclear triad, and you’re running for president of the United States, you’d better have a good answer,” Bush said on Wednesday.

Bush’s promise not to launch a third-party campaign is a window into the unexpected turn that the race for the Republican nomination has taken since Trump announced his candidacy. In September, the Republican National Committee asked the candidates to sign a pledge that they would not launch a third-party campaign against the Republican nominee—a decision that was widely assumed to be calculated with Trump in mind. But with the real estate mogul’s popularity surviving long past expectations, Bush’s insistence that Trump fever will fade in favor of the establishment candidate is becoming less convincing.