As discussed in detail in the daily video on MBS Live, today's bond market weakness was multifaceted, to say the least.  But if we want to make the move higher in stocks and bond yields about one thing and one thing only, we can continue to talk about the prospects for the tax bill passing.  In that regard, today's big to-do was a change of heart from Senator McCain who previously said he wouldn't vote for the bill.  Now he will, and that gives the Senate enough votes to try to pass the thing tonight or tomorrow.

The rally in the stock market was more gradual and lasted longer than the mover higher in bond yields.  It was also much bigger relative to recent ranges.  The exuberance in stocks, alone, could explain some of the weakness in bonds as investors sell bonds to buy stocks.

Even then, the move in bonds doesn't really need much more explanation than this: yields were very close to key technical levels and today was the last trading day of the month.  It wouldn't really matter what stocks were doing if month-end tradeflows in bonds happened to be skewed in favor of sellers (something that could easily happen if traders did too much "month-end" buying earlier in the month due to the holiday.