President Obama has quietly promised Massachusetts Sen. Elizabeth Warren complete support if she runs for president — a stinging rebuke to his nemesis Hillary Clinton, sources tell me.

Publicly, Obama has remained noncommittal on the 2016 race, but privately he worries that Clinton would undo and undermine many of his policies. There’s also a personal animosity, especially with Bill Clinton, that dates from their tough race six years ago.

A former Harvard law professor and administration aide, Warren would energize the left wing of the Democrat Party just as Obama did against Clinton in 2008.