The battle for control Senate has turned into trench warfare. With five months until the elections, both parties mostly agree on the battlefield and neither sees a coming partisan wave washing the other out of contention.
Still, the map has shifted and it's time to update the National Journal Big 10, our blue-chip index of contests that will determine control of the Senate. The list is getting its first makeover since it was unveiled in March: Gone is Maine (where both sides are all-but-conceding to independent Angus King, who is expected to caucus with the Democrats). And in North Dakota the Democrat is off to a surprisingly competitive start in the deep-red state.
Here are the state affairs for the races, broken into three categories - the embattled incumbents (most vulnerable), the battling incumbents (less vulnerable) and the open seats - each ranked in order of likelihood that they flip party control.
The embattled incumbents:
Missouri: (Incumbent: Sen. Claire McCaskill (D))The question in Missouri is how well can McCaskill swim upstream against an anti-Obama tide. She won't learn who her GOP opponent is until August -- Rep. Todd Akin, former state Treasurer Sarah Steelman, and businessman John Brunner are competing for the nod -- but Republicans are confident whoever emerges will be the frontrunner this fall. McCaskill will begin the fall campaign with a huge cash advantage -- she had more than $6 million banked at the end of March -- but outside spending has leveled the playing field, with GOP-leaning groups spending about $6 million in anti-McCaskill ads as of the end of May.
Montana: (Incumbent: Sen. Jon Tester (D))
In the early goings of the campaign, Tester just wants to make sure Montanans don't think he's gone Washington. His early TV spots feature guns, tractors and wide-angle images of farmland. "I'm focused on doing what's right for Montana -- always," he says in one such spot. His opponent, Rep. Denny Rehberg, works in Washington too, but Rehberg has the advantage of running as a Republican in a red state in a presidential year. The sparsely populated state is expected to be flooded with money all the way through November, if only because the airwaves are so cheap in Big Sky country. Already, more than $3.5 million in outside groups ads have been aired in the state.
Massachusetts: (Incumbent: Sen. Scott Brown (R))
The Elizabeth Warren Native American controversy is the story that just kept on dripping. Every few days another headline seemed to emerge, or Warren would make another admission that prolonged questions about why she ever listed herself at Harvard as a minority faculty member. Brown, the Republican incumbent, meanwhile, has tried to do everything but talk about specific policies to pump up his favorables. As the Boston Celtics advanced in the playoffs, he even unveiled a minute-long radio ad that touted his love of the sport and the team -- and didn't even mention the fact that he is running for Senate until the disclaimer. To win, he'll have to win among Republicans, independents and even take a sizable chunk of Democrats -- and so far he's hoping sports is the ticket.