Joe Biden might be leading the race for his party's nomination now, but the former vice president is a "walking time-bomb" and has to perform a "high-wire act" if he is to emerge from the crowded Democratic field in first place, according to Brit Hume.

Hume, Fox News' Senior Political Analyst, made the comment while discussing Biden's 2020 prospects on the latest episode of the Fox News podcast, "The Candidates with Bret Baier."

"I like Biden on a personal basis, but I think he is a walking time-bomb," Hume said. "I think his age is an issue, I’m the same age as he is, my age is an issue, I think his is too... the filters don’t work as well, the memory isn’t as sharp.

"You might blurt out things as he did the other day when he said China is no competitor of ours. Now, I can kind of get where he was coming from on that, meaning you know we are the best and nobody can beat us. But that’s not how it came out and that is not how he said it.

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"He is gaffe-prone and always has been and I don’t think that he’s less-so now. He’s got a lot of strengths, he’s got a huge body of sympathetic support in the party, and he’ll be able to raise money. He’ll be in this, but it’s a high-wire act and I’m not sure he can make it.”

Hume also didn't put complete faith in Biden's substantial lead in polling, noting how early Democrats were in the race for their party's nomination. The former VP consistently outpolled his Democratic competitors -- even before he announced his candidacy -- and, according to a Fox News poll conducted in May, Biden led the pack with 35 percent of the support of Democratic primary voters.

Amy Walter, National Editor of the Cook Political Report, had a more positive view of Biden's bid to win the Democratic nomination but agreed with Hume he does not have an easy path.

“I think right now he looks like the safest choice for Democrats," Walter said on "The Candidates."

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"That’s what I hear over and over again when I talk to Democrats, ‘It’s just not risky, we don’t want to, we’re really risk-averse right now, this is not the time to take a chance on someone, this is the time to go with somebody that would’ve won last time.’

"But I think Brit is exactly right, now he has to go through and see if he can handle these waters that he’s swimming in that are very different. He was last on the ballot by himself... 2007? 2008? That’s a long time. You can hear the rustiness in that Pittsburgh speech and to be fair everyone starts a little rusty. That’s ok.”

Josh Kraushaar, Political Editor at National Journal, said he believes Biden is "going to be his own worst enemy."

"I think if he can run as a credible candidate, not make a whole lot of gaffes, he’s a frontrunner," Kraushaar said.

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"But I don’t think there’s a lot of confidence in the Democratic universe that he’s gonna be able to do that for over a year. He’s made a lot of mistakes so far... you look at national polls, they show Biden in the lead but, they also show the biggest concern, or one of the biggest concerns in one’s voting preference is just being over 70 years old or being the oldest candidate, one of the oldest in the field.

"[Those are] big vulnerabilities that are not being priced into his support right now. So he does have a long way to fall.”

Listen to the full interview on the latest episode of "The Candidates with Bret Baier" here, and subscribe to the podcast on iTunes.