Looking good so far:

Republicans must defend 19 seats including six (North Carolina, Iowa, New Hampshire, Florida, Pennsylvania and Ohio) in states won by President-elect Barack Obama earlier this month.

Democrats have far less vulnerability; only one incumbent up for re-election (Colorado Sen. Ken Salazar) won with less than 55 percent of the vote in 2004 and several potential races are entirely contingent on one Republican candidate deciding to run.