Pundits wrote off Sen. Bernie Sanders’s campaign back in October after his heart attack evoked the risks of nominating a candidate who would turn 80 during the first year of his presidency.

But since then, Sanders has made a remarkable comeback — and not just in terms of his health. Having climbed to second place nationally and raised a whopping $34.5 million in the fourth quarter, he now finds himself leading in New Hampshire and tied for first place in Iowa, according to the latest CBS/YouGov poll.