I personally don't think these midterm elections were a mandate for Republicans as much as people were unhappy about the economy and jobs and voted for the party that wasn't in power. In 2008 Obama and the Democrats claimed they had a mandate (and by their majorities in each chamber of Congress, they technically did) and then they bungled things up and the voters paid them back for it.
As much as I would like to put the current state of affairs in the lap of one party or administration, the problem lies in the increasing bipartisan atmosphere in Washington and the willingness of each party to sabotage the policies of the other regardless of whether or not it would be good for the country.