Joe Biden has told some top Democrats he’s definitely running for president, and even threw out Jan. 15 — next Tuesday — as a target announcement date.

“If I’m walking, I’m running,” he has told friends winkingly.

What they’re saying: His youngest brother, Frank Biden, thinks the former vice president is in. Ditto for some advisers. Several Democrats, including Michael Bloomberg and Terry McAuliffe, are watching him as their most formidable potential competitor.