William Cummings

USA TODAY

Libertarian candidate Gary Johnson had another tough night on the campaign trail when he couldn't come up with the name of a foreign leader during an interview Wednesday.

"Who's your favorite foreign leader," MSNBC's Chris Matthews asked Johnson, who sat beside his running mate, former Massachusetts governor Bill Weld.

Matthews pushed Johson to pick anyone, from any continent or country, after an apparently confused Johnson repeated the question.

"Name one foreign leader that you respect and look up to," Matthews said. "Anybody," he added as Johnson searched for an answer.

"Mine was Shimon Peres," Weld offered, picking the former Israeli leader who died Wednesday from a stroke.

"I'm talking about living," Matthews said, pointing back to Johnson.

"You gotta do this," Matthews said. "Anywhere. Any continent. Canada, Mexico, Europe, over there, Asia, South America, Africa: Name a foreign leader that you respect," Matthews said as Johnson continued to fumble for an answer.

"I guess I'm having an Aleppo moment," Johnson said — referring to a much-lampooned moment in an interview earlier this month, where he responded "What is Aleppo?" when asked what he would do about the Syrian city that has been decimated by civil war.

"But I'm giving you the whole world," Matthews said. "Anybody in the world you like. Anybody. Pick any leader."

"The former president of Mexico," Johnson said.

"Which one?" Matthews asked.

"I'm having a brain freeze," Johnson said as Weld began to shout out the names of recent Mexican presidents.

"Fox! Thank you!" Johnson said when he finally heard the name of former Mexican president Vicente Fox, which he had been searching for.

When asked his favorite leader, Weld quickly responded with German Chancellor Angela Merkel.

Late Wednesday Johnson's campaign manager Ron Nielson posted on Facebook that the gaffe was not a big deal and Hillary Clinton and Donald Trump's supporters were just trying to exploit it.

"The Clinton and Trump supporters are at it again. This is gotcha-ism at its finest. Not by Chris Matthews, but by too many looking for any opportunity to pounce. Anyone who watched the entire hour tonight on MSNBC saw Governors Johnson and Weld answer every question and deal with the entire spectrum of issues. A very fine performance," Nielson said. "Yes, asked to name a favorite foreign leader, Gov. Johnson didn’t quickly name a specific favorite. That really doesn’t mean much. Most Americans and certainly most political candidates would have to stop and think before responding, with the possible exception of a Donald Trump who is enthralled by Putin."

Gary Johnson swings and misses on Syria, asking 'What is Aleppo?'