WaPo:

As Congress returns this week, Mitch McConnell remains the one-man roadblock for Democrats’ election security bills. He’s still refusing to allow a vote, even as Democrats deride him as “Moscow Mitch” and accuse him of inviting Russia to interfere on Republicans’ behalf in the 2020 election. 

But why is McConnell so staunchly opposed? 
Republicans and Democrats offer a fairly straightforward theory: McConnell is wary of drawing the ire of President Trump, who has repeatedly wavered on whether Russia interfered in the presidential contest — and seems to view traditionally bipartisan discussions about election security as delegitimizing his unexpected 2016 victory over Hillary Clinton.

“This is a narrative that the White House doesn’t want to approach,” David Jolly, a former Republican House member from Florida and an outspoken Trump critic, told me. “The president’s not comfortable talking about it. He’s someone with a fragile ego. And McConnell is happy to coordinate with this White House. That’s the only thing that explains it.”