In an effort to salvage the seat, the National Republican Senatorial Committee placed a $600,000 media buy for 2,000 gross ratings points for the next two weeks. The party's chances there lie in the makeup of the contest. With a three-way race, Secretary of State Charlie Summers (R) doesn't need 50 percent to win, but he needs state Sen. Cynthia Dill (D) to take a significant portion of the Democratic vote.
The next challenges for Republicans are defending seats in two tossup races: Nevada Sen. Dean Heller (R), appointed by Gov. Brian Sandoval (R) earlier this cycle, against Rep. Shelley Berkley (D); and Massachusetts Sen. Scott Brown (R) against Harvard professor Elizabeth Warren (D). Obama is favored in both states, but in the Bay State to a far greater degree. Other races to watch are for GOP open seats in Arizona and Indiana.
In the Hoosier State, Democrats see a chance for Rep. Joe Donnelly (D) against state Treasurer Richard Mourdock (R), as Democratic outside groups have recently hit the airwaves on Donnelly's behalf.
The Republicans' absolute bottom line path to the majority includes three states Obama won't win. The GOP must defeat Montana Sen. Jon Tester and pick up open, Democratic-held seats in Nebraska and North Dakota. If the GOP misses on any of those, a Republican majority would be highly unlikely.
All three are winnable propositions for Republicans, but two of them are pure tossups. Strategists in both parties have complimented the smart campaign Tester has run against Rep. Denny Rehberg (R), who's won six straight statewide federal races. Meanwhile, former North Dakota Attorney General Heidi Heitkamp (D) has consistently held a small lead or been tied with Rep. Rick Berg (R) in internal Democratic polling.
If Republicans are successful in those three states, as the party believes it will be, focus then turns to two presidential battlegrounds: the Wisconsin race between Rep. Tammy Baldwin (D) and former Gov. Tommy Thompson (R) and the Virginia battle between former Govs. Tim Kaine (D) and George Allen (R). Should McCaskill triumph and the GOP lose only Maine, taking the majority would require Republicans to win both.
Republicans are optimistic in Virginia and Wisconsin, the latter a hotbed of partisan politics for the past year. However, coming off a late primary, Thompson just got his first hit from national Democrats. The Democratic Senatorial Campaign Committee launched its opening salvo in the Badger State on Wednesday, the start of a $5.2 million commitment to help keep the seat of retiring Sen. Herb Kohl (D).
Virginia has been one of the top targets of spending at both the presidential and Senate levels, including a $1 million ad campaign launched against Kaine by Crossroads GPS on Tuesday. As of last week, the DSCC had $8.1 million in fall TV time reserved in Virginia, and the NRSC had about $5.5 million reserved. Observers on both sides believe it's unlikely Allen will win if Romney doesn't.
Vice President Joe Biden waits to conduct a mock swearing-in ceremony with Sen. Brian Schatz, D-Hawaii, in the Capitol's Old Senate Chamber, December 2, 2014. Schatz was sworn in to serve the remainder of his term since he was appointed to the seat after Sen. Daniel Inouye, D-Hawaii, passed away.