WASHINGTON — Senate negotiations aimed at striking a bipartisan deal to revive expired funds under the Affordable Care Act — or Obamacare — have fizzled, according to senators involved and sources with knowledge of the discussions. The odds of a deal have been slim for months. Now, on the day that ACA open enrollment ends , even the optimists have grown pessimistic as the working group falls behind its self-imposed timeline. The Senate left town Thursday for a one-week recess. Democrats are