Harold Ford Jr. ventured to the suburbs yesterday to test the waters outside New York City for a possible US Senate bid.

The ex-Tennessee congressman visited with patrons and local Democrats at a Rockland County diner, the first of several stops planned in the suburbs and upstate as he decides whether to challenge Sen. Kirsten Gillibrand in the Democratic primary this fall.

“I continue to learn,” said Ford who also called this week’s Massachusetts election upset a “wake-up” call for Democrats and incumbents.

“Anyone who believes they are safe this morning as an incumbent is probably kidding themselves,” he said.