Dem Momentum: Just a "Vibe Shift," Or Something Real?

Numerous data points are suggesting that there may be some positive trends for Democrats, along with some troubling signs for Republicans.  Dems have been acting downright giddy about what they see as the recent turn.  But is it mostly in their mind?  Is it going to be enough? Or are they getting meaningful traction at just the right time? The panel weighs what we're seeing out there and separates what's real from what's not.