A tidal wave that swept Republicans back into control of the House was not strong enough to do the same in the Senate. Despite losing a handful of seats to GOP candidates, Democrats will retain control of the Senate in the 112th Congress, albeit with a reduced majority.
Democrats had actually appeared in a position to add to their numbers early in 2009, when several Republican senators announced they would retire at the end of their terms. That April, Pennsylvania Sen. Arlen Specter announced he would abandon the GOP and seek reelection as a Democrat, which, when Minnesota Democrat Al Franken was seated after a prolonged recount, assured the party of a 60-vote supermajority.
That advantage would prove fleeting. Lengthy negotiations aimed at securing some Republican support for a healthcare overhaul pushed final consideration well beyond the summer deadline Democrats had hoped for. The death of Edward M. Kennedy, the Senate's "Liberal Lion," spurred a special election won by Republican Scott Brown on the promise of being the Senate's "41st vote" to block health reform.
Even faced with that once-unthinkable upset, the White House pushed ahead on healthcare, ultimately passing it through the legislative tactic known as reconciliation. Obama signed the bill into law in March.
The months that followed were marked by Republican primaries for Senate in which establishment favorites were upset by "tea party" candidates running in part on a platform of repealing the health law. In Kentucky, Rand Paul toppled the hand-picked candidate of Senate Republican Leader Mitch McConnell. In Nevada, former Assemblywoman Sharron Angle surged against two other candidates, including the former state Republican chairwoman.
The two biggest upsets came late in the calendar. In August, Alaska Sen. Lisa Murkowski lost to Sarah Palin-backed challenger Joe Miller. Weeks later, popular Delaware Rep. Mike Castle fell to Christine O'Donnell, a political gadfly who successfully branded Castle as "Republican in Name Only."
Democrats thought victories by these more conservative candidates would help them hold on to enough seats to remain in the majority. But the playing field only continued to expand, as once-popular senators like Wisconsin's Russ Feingold, Washington's Patty Murray and California's Barbara Boxer, faced an unusually hostile political climate.
The role of unregulated spending from third-party groups, some of which are not required to disclose their funding, also put Democrats at a competitive disadvantage financially.