President Donald Trump ridiculed Democrats on Tuesday for a renewed impeachment effort in the House of Representatives, suggesting it was a sign they were worried about him winning re-election.

“I think it’s ridiculous. It’s a witch hunt. I’m leading in the polls. They have no idea how they stop me,” Trump said. “The only way they can try is through impeachment.”

Trump argued that beginning impeachment hearings over a phone call with a foreign leader was unprecedented.

“This has never happened to a president before,” he said.

The president commented on the issue as he arrived at the United Nations Assembly on Tuesday ahead of his speech to world leaders.

Democrats and the establishment media are driving the narrative that Trump may have frozen military defense spending for Ukraine as part of a quid pro quo to get officials to investigate former Vice President Joe Biden’s son. The president has denied it.

Trump said his phone call with Ukrainian President Volodymyr Zelensky was “perfect” and that there was “no pressure put on them whatsoever.”