In the most recent 2010 “generic Congressional ballot” survey by Gallup, Republicans lead Democrats 48-44 among registered voters.
These are good early poll numbers for Republicans, but they still have a great uphill battle to fight. Not only would this kind of small margin translate to modest gains in the House and Senate, but the Democrats still hold the ultimate trump card: the economy. If the economy remains the most important issue for voters, then a full economic recovery (most importantly, low unemployment) by next November would have propitious consequences for Congressional Democrats.