5. Alaska (Democratic-controlled)
Joe Miller's fall from grace within the Alaska GOP is one bit of encouraging news for Senate Republicans. A PPP poll confirmed the state intel: The erratic tea-party favorite faces long odds against the early favorite, Lt. Gov. Mead Treadwell. The survey also found Democratic Sen. Mark Begich polling at only 44 percent, a low number, against Treadwell. Also: Keep an eye on Alaska's Natural Resources Commissioner Dan Sullivan, a Marine Corps lieutenant colonel who recently deployed to Afghanistan. Republican operatives in Washington think his biography is more compelling than that of the low-key Treadwell.
Alaska polling is notoriously volatile, and Begich is still well-liked. But as in Arkansas, the national environment could be the decisive factor here if Republicans nominate the right candidate. Expect Democrats to focus on Begich's Alaska roots, in contrast to Treadwell and Sullivan, who grew up in the lower 48.
6. Louisiana (Democratic-controlled)
Mary Landrieu's seat could be the Democratic firewall to protect the party's majority. Despite the state's conservative electorate, she's a strong incumbent, with a history of outperforming early expectations. Her brother's popularity as mayor of New Orleans should help Landrieu win a little crossover support. And she benefits from Louisiana's unusual election rules, where all candidates compete on the same November ballot and head to a runoff if no one wins 50 percent. That could mean the GOP front-runner, Bill Cassidy, will have to focus efforts on protecting his right flank rather than taking on Landrieu full time.
7. Kentucky (Republican-controlled)
Republicans are as nervous as ever about McConnell, even though they view him as the favorite. His own polling shows him with middling approval ratings, and he faces a well-funded challenger (Matt Bevin) on his right. In Alison Lundergan Grimes, the Democrats have a dynamic candidate who should make this a competitive race until the end. Her biggest challenge is distancing herself from President Obama, his health care law, and the national Democratic positioning on energy, all of which are toxic in Kentucky. There's a reason her campaign slogan is "Team Switch." If the race becomes a referendum against McConnell, she can win. If her stances on issues become the focus, it becomes a lot harder.
8. North Carolina (Democratic-controlled)
Comparing the vulnerable Southern Democratic senators, there are two schools of thought among strategists. Some posit that Kay Hagan is more vulnerable than Landrieu and Pryor because she's the least experienced and isn't well-known. Others believe her anonymity could be an asset and that she stands to benefit from North Carolina's changing demographics in favor of Democrats.
Hagan's biggest asset may end up being the middling quality of the Republican opposition. The early front-runner, state House Speaker Thom Tillis, has seen his campaign defined early on by the Legislature's rightward turn. He'd much rather be talking about his previous business background and the economy, not the GOP's restrictions on voting accessibility. If he can't rebound with a stronger message or if Republicans don't land a more compelling alternative, Hagan may be in for a smoother ride than expected.