The Overton Window, as I understand, refers the ideas acceptable to the mainstream, those ideas NOT considered radical left or radical right.
The key here is mainstream. There is no longer a mainstream. The issue is among the people as much as it within the two major parties. Let's be clear, before 2000, the vast majority of politician (and voters)
in congress were within the mainstream.
Now, we have the Republicans controlled by Trump, who has moved far, far from any mainstream set of ideas pre-2000. There are those within the mainstream in the PArty, but few can stand up to Trump. Trump includes his PAC war chest every day. He will support primary opposition to anyone who in any way opposes him. Maybe the few in the Senate will work with a few Democrats and form the group that negotiates legislation. Perhaps this can last, likely not.
In the Democrats, we have lots of those who are centrists within pre-2000 definitions. They easily could work with the those with the ideas of Nixon, Reagan, Bush, Bush, Dole, McCain, and yes, McConnell.
HOWEVER, and it is a big however, the leftists may finally have a chance to take over the party. The key to their success will be that their greatest strength with voters will be their unabashed opposition to working with Republicans on anything. This effort has failed several times iin the last 100 years, but there was never a opposition like the current Republican Party.