It’s “quite possible” Exxon Mobil CEO Rex Tillerson won’t be confirmed due to concern over his ties with Russia, a Democratic senator said Thursday.

Sen. Chris Coons, D-Del., said on CNN Tillerson may face an uphill battle due to concerns expressed by GOP Sens. Marco Rubio, Lindsey Graham and John McCain, among others. He said Tillerson’s nomination speaks to Trump’s problem of seeming to be moving closer to Russia, an openly adversarial state in recent years.