Vice President Biden knows political observers are watching him, tracking his every move and parsing his every word as he weighs a late-breaking presidential bid. It is not yet clear what his announcement will be. It is clear that he may be enjoying the feverish pre-announcement speculation.

On Wednesday, Biden wrapped up a roughly 20-minute speech to a group of labor leaders at the White House following a daylong summit about boosting wages for the middle class.

“We need your muscle, we need to move," Biden told the group. Then, shifting from a deeply serious thought, he made a crack about needing to leave the podium so the labor activists could get to their next appointment, with President Obama.

"If I don’t move, I’ll be demoted to secretary of state or something," he said, as a slow-motion wave of surprised laughter drifted across the room. "That’s a joke! That's a joke. That's a joke."

Of course, that particular punch line could fall a bit flat with his potential 2016 rival: former secretary of state Hillary Rodham Clinton.

Earlier Wednesday, Clinton herself said that if she faced Biden in the primary, she wouldn't automatically go on the attack. "If he gets in, I will continue speaking positively about him," she told PBS anchor Judy Woodruff.