He will never resign and his district is ultra liberal so he is safe. BUT, he should immediately have his clearance removed and prohibited from having access to any classified information or entring the SCIF in the House basement. And, that is just for starters.
bttt
Electorally, he is safe, alright, Hollyweirdistan being what it is. But Congress can determine not to seat a member who has behaved unethically. No chance during this Congress, but should the Republicans ride into control of the House on Trump’s coattails, immediately after the formalities, he should be frog-marched out the door and thrown into the street on his ear.