Hillary Clinton is picking up another Republican endorsement, this time from former Virginia Senator John Warner.

Warner is set to appear Wednesday morning with Democratic vice presidential nominee — and current Virginia senator — Tim Kaine in Arlington.

Warner served five terms in the Senate and has strong national security credentials. He is a former Navy secretary and Senate Armed Service Committee chairman.

Warner's endorsement strengthens Clinton's argument that she is better prepared to handle national security and foreign policy than rival Donald Trump.

Warner and Clinton served together briefly in the Senate. He retired in 2009.

Clinton's campaign says this is Warner's first time endorsing a Democratic presidential nominee. She says she's honored Warner would trust her "with the weighty responsibility of being Commander in Chief."