During a Washington fundraiser for Democrat Ed Markey in his bid to be Massachusetts' U.S. senator, Biden said Markey would "command respect and attention the moment he stands on the floor to speak for the first time."
Markey, who represents Massachusetts in the U.S. House, faces Republican Gabriel Gomez in a June 25 contest to succeed John Kerry, now secretary of state.
Biden cautioned about being complacent.
"Barack Obama's not at the head of the ticket. And that means those legions of African-Americans and Latinos are not automatically going to come out," Biden said.
"No one has energized them like Barack Obama. But he's not on the ticket. So don't take this one for granted," the vice president said.
"Please, don't be asking yourself two months from now, 'God why didn't I do more?'"
Tthe GOP drew Biden's ire.
"This is not your father's Republican Party," Biden said. "There's never been as much distance ... between where the mainstream of the Republican congressional party is and the Democratic Party is. It's a chasm."
Biden said he wasn't questioning the character of conservatives Paul or Cruz, but commented, "The last thing in the world we need now is someone who will go down to the United States Senate and support Ted Cruz, support the new senator from Kentucky ... Think about this. Have you ever seen a time when two freshman senators are able [cow] the bulk of the Republican Party in the Senate?"
During the gun control debate, Biden said, nine of the 17 senators he called were Republicans and none "offered an explanation on the merits of why they couldn't vote for a background check. But almost to a person, they said, 'I don't want to take on Ted Cruz. I don't want to take on Rand Paul.'"
"They're not bad guys. They don't get it," Biden said. "But Ed does. In his gut, Ed gets it."