Sen. Bernie Sanders (I-Vt.) warned Friday that President Trump may not concede if he loses the general election in November.

“This is not just idle speculation,” Sanders told Politico. “Trump was saying … ‘the only way they can take this election away from us is if this is a rigged election.’ Now he is making that statement at a time when virtually every national poll has him behind.”

The progressive firebrand and former presidential hopeful pointed to comments Trump made during the GOP convention last month.

In a July interview with FOX News’s Chris Wallace, Trump also said he’ll “have to see” if he would accept the results in November.