Bond markets began the day roughly unchanged after initially improving in the overnight session.  Domestic hours saw 10yr yields make 2 attempts to break higher with both thwarted by 2.345%.  Just after the 2nd bounce, the first leaks started coming out regarding the Senate tax plan.  Markets responded with a "risk-off" trade (stock prices and bond yields both moved lower).  

Bonds would get one final boost from a relatively strong 30yr bond auction.  The ensuing move brought 10yr yields as low as 2.315, but that's where the good news ends.  Broader financial markets were already in the process of trading the tax reform news BACK in a "risk-on" direction (stock prices and bond yields higher).  That meant bonds had some catching up to do. Longer-term yields rose steadily throughout the afternoon.  Both MBS and Treasuries ended the day in negative territory near their weakest levels.