Sen. Bernie Sanders, I-Vt., will play a "major role" in the 2020 presidential election, his wife Jane Sanders said Monday.

"What we hope is his vision will carry the day in 2020 whether he's the candidate or not. He will be playing a major role," Jane Sanders said on Fox News.

Initially dismissed as an incidental figure in the 2016 Democratic primary race, Bernie Sanders ultimately mounted a serious challenge to Hillary Clinton, particularly with his popularity from younger voters. When asked if anyone in the potential 2020 field could generate crowds like her husband did, Jane Sanders responded, "We don't know."

Bernie Sanders would be the oldest president in history if he were to run and win in 2020.

"I think if age was the way it was across the board and everybody at 79 acted the same way, maybe. Bernie exhausts me. I can't keep up with him," Sanders said. "The young people in his office can't keep up with him. I don't know whether it was because he was a long distance runner but he's got the energy of a 40-year-old and the brilliance like Bernie Sanders."