Former vice president Joe Biden continues to hold a lead among Democratic presidential aspirants, a new poll showed Sunday, despite recent questions about his age and mental clarity.
Biden's lead among Democratic voters has remained relatively steady, as he and senators Bernie Sanders and Elizabeth Warren increasingly emerge as a distinct top tier in the large field, according to the Washington Post/ABC News poll.
The poll showed Biden favoured by 29 per cent of registered Democrats or Democratic-leaning independents, with Sanders at 19 per cent and Warren, who has been surging, at 18 per cent.
The survey of registered voters was conducted for four days through Thursday -- the day when Biden's age and energy levels came under their most direct attack yet from any of his Democratic rivals.
"I just think Biden is declining," Ohio congressman Tim Ryan told a Bloomberg News reporter in a phone call.
"I don't think he has the energy. You see it almost daily. And I love the guy."
One former Democratic candidate, 38-year-old Eric Swalwell of California, was more blunt, however, noting during a Democratic debate that he was six years old when Biden, then a senator, said that "it's time to pass the torch to a new generation."
Asked on Sunday about Ryan's comment, Senator Amy Klobuchar demurred, telling a CNN interviewer, "I'm running my own campaign."
But the 59-year-old Klobuchar quickly added: "I have a lot of energy. I'm someone who never stops working."