Update: An earlier version of this story incorrectly described Sen. Bill Nelson's status. He is running for re-election.
After a few months during which a huge number of races resembled real tossups, we've reached a point in the battle for control of the Senate in which we can start creating tiered groups out of our top 10 -- call them the flippers, the coin tosses and the leaners.
The flippers (Nebraska, Maine and North Dakota) are the seats most likely to change party hands in November. The coin tosses (Missouri, Montana, Massachusetts, Wisconsin) are races in which there's no clear front-runner. And the leaners (Nevada, New Mexico and Virginia) are states in which the incumbent party has an advantage in the fight to keep the seat. We see the remainder of our top 20 favoring the incumbent party by much wider margins.
In this, the sixth installment of Hotline's monthly Senate rankings, we examine the seats most likely to change partisan control in next year's elections. That is, we see Sen. Ben Nelson's seat in Nebraska as more likely to wind up in Republican hands than Sen. Kent Conrad's seat in North Dakota (but not by much), and Scott Brown more likely to lose to a Democrat than Sen. Dean Heller of Nevada. Our complex methodology includes a delicate balance of poll numbers, both public and private; fundraising performance; message resonance; buzz on the trail; and, the key ingredient, our gut feelings. From those five factors, we answer a fundamental question: Which candidate would we rather be? In North Dakota, we'd rather be Rep. Rick Berg than former Attorney General Heidi Heitkamp, for example.
The ultimate conclusions are subjective, of course. But they represent months of close scrutiny of each race and our best conclusions as to where the Senate is headed in the 113th Congress.
|NEBRASKA (Open D, Sen. Ben Nelson retiring) (Last month's rank: 1)
Democrats just came out of the field with a poll in Nebraska. Republican polls show state Sen. Deb Fischer leading former Sen. Bob Kerrey by a wide margin. Democrats are probing for weaknesses in Fischer's background and Republicans say they expect to spend at least a little money here, but at the moment this looks like a near certain GOP pickup.
|MAINE (Open R, Sen. Olympia Snowe is retiring) (Last month: 3)
Republicans and Democrats are taking a wait-and-see approach in Maine. Republicans will pick their nominee on June 12, while national Democrats are throwing in their lot with former Gov. Angus King, an independent, even though they'll have a nominee of their own. Donors have gotten the message that King is the de facto Democrat; don't expect the winner of next week's primary to pull off a big fundraising quarter.
|NORTH DAKOTA (Open D, Sen. Kent Conrad is retiring) (Last month: 2)
Democrats tout three consecutive polls that have former Attorney General Heidi Heitkamp leading Rep. Rick Berg, and Republicans acknowledge it's a surprisingly close race. But in a deep red state, Heitkamp is going to need a large number of voters who check Mitt Romney's name at the top of the box. If this is a popularity contest, Heitkamp has a better-than-even shot. If voters associate Heitkamp with President Obama, Berg will be a senator.
|MISSOURI (D, Sen. Claire McCaskill) (Last month: 4)
McCaskill has already started heradvertising campaign, and it's having a positive impact on her numbers, according to Democratic sources. A competitive Republican primary means McCaskill is hanging out there all alone, vulnerable to attacks from outside Republican groups without being able to hit anyone back. But the primary is producing ample fodder, and the winner -- likely either businessman John Brunner or former Treasurer Sarah Steelman -- will face an immediate onslaught of McCaskill attacks the moment the results are known after the August 7 primary. Expect Republicans to bring up what they call Air Claire, the private jet for which McCaskill was reimbursed with taxpayer dollars before she refunded the money; that line of attack hasn't featured in any Republican paid media yet.
|MONTANA (D, Sen. Jon Tester) (Last month: 5)
Like McCaskill, Tester is on television with positive spots -- and it's boosting his image. Tester is running one of the better campaigns of the cycle, while his rival, Rep. Denny Rehberg, isn't getting his message across as effectively. Rehberg has to tear down Tester's image as the good-guy Montana farmer, something he hasn't done yet, to his own side's chagrin.
|MASSACHUSETTS (R, Sen. Scott Brown) (Last month: 6)
After a month of headlines about her Native American heritage, one would surmise consumer advocate Elizabeth Warren would have taken a hit in public polling. Her unfavorable ratings have creeped up, but her toplines haven't fallen, and she's still neck-and-neck with Sen. Scott Brown. Democrats think she's turned the page on the bungled month; Republicans say Brown still has a chance to use the story to sew doubts about Warren among critical conservative and Catholic Democrats who will have to cross over to give Brown a full term.
|WISCONSIN (Open D, Sen. Herb Kohl is retiring) (Last month: 7)
Former Gov. Tommy Thompson leads the Republican field now, but sources say that's going to be short-lived. Both sides expect either ex-Rep. Mark Neuman or businessman Eric Hovde to win the August 14 primary. The winner will face Rep. Tammy Baldwin in a race that's likely to pit a candidate who's too liberal for the state against a candidate who's too conservative for the state. Neither side has a really good handle on the dynamics, and the race has been under the radar thanks to the gubernatorial recall. Now that Gov. Scott Walker has kept his job, expect the outside assault on Baldwin to begin shortly. Still, this race is as close to a pure tossup as exists right now.
|NEVADA (R, Sen. Dean Heller) (Last month: 8)
Sen. Dean Heller has opened a small but static lead over Rep. Shelley Berkley, who's plagued by an ethics investigation that's hanging over her head. Still, there may be no race more closely tied to the presidential election in a state that's changing so dramatically on a demographic level. But campaigns matter, and right now Heller is running the better race.
|NEW MEXICO (Open D, Sen. Jeff Bingaman retiring) (Last month: 10)
Both sides got the candidates they wanted in Tuesday's primaries, and without too much of the intra-party feuding that once looked certain in two Anglo-vs.-Hispanic contests. Ex-Rep. Heather Wilson not only needs to win crossover votes, she needs to win a large number of Hispanics at a time when her party's image in that community is at a nadir. Wilson is the best possible candidate for that job; she routinely ran ahead of the rest of her party when she was in Congress. Still, Rep. Martin Heinrich is the slight favorite.
|VIRGINIA (Open D, Sen. Jim Webb retiring) (Last month: 9)
Former Gov. Tim Kaine's campaign has built a financial edge over ex-Sen. George Allen from the start, and he's putting that money to good use by reserving late airtime early. Republicans will try to paint Kaine as President Obama's lackey, but that may even work to Kaine's advantage in the presidential race's top battleground state, given Obama's turnout efforts. Allen faces little more than token opposition in next week's primary, and the vast majority of voters know both candidates well.
|OHIO (D, Sen. Sherrod Brown) (Last month: 12)
When someone spends $6.5 million to define you, your negatives are going to rise. That's what's happened to Brown, who's running ahead of Treasurer Josh Mandel by a narrower margin than he had been last month. But Brown did his own defining, running ads labeling Mandel a career politician and choosing images that make the 34-year old look young. While Mandel's top-line numbers have risen, Brown's are still hovering at or above the 50-percent mark.
|FLORIDA (D, Sen. Bill Nelson) (Last month: 11)
Republicans are frustrated with the lack of progress Rep. Connie Mack is making in his battle against Nelson. Mack runs close to Nelson in private and public polling, but GOP operatives are scared by the $8 million financial edge Nelson's built. In a state with so many hot races, Nelson will be able to buy his way onto television, while Mack will be stuck with an empty bank account after the August 14 primary, and Mack's allies are likely to be shut out of the advertising market. Nelson will outperform President Obama along the I-4 corridor and in the Panhandle -- a necessity given Obama's uphill battle to hold the state.
|ARIZONA (Open R, Sen. Jon Kyl retiring) (Last month: 15)
Rep. Jeff Flake clearly has a problem: Businessman Wil Cardon's numbers are rising, thanks to the money he's investing in his own race. Cardon still trails by double digits, but he's got until August 28 to make his case, which he's doing currently by blasting Flake's record on immigration. Flake's friends at the Club for Growth are jumping in now, but Cardon is still likely to outspend Flake and his allies before August. A Cardon win would give former Surgeon General Richard Carmona a better shot; either Republican, however, would still be at least a slight favorite.
|INDIANA (R, Sen. Richard Lugar defeated in primary) (Last month: 16)
Democrats are in the field with a survey at the moment, and they're confident Lugar's primary loss to Treasurer Richard Mourdock makes the seat markedly more competitive (Republicans agree, but not to the same degree). Rep. Joe Donnelly hasn't raised good money; he needs a strong quarter to effectively play himself into the race before outside groups will come to his aid.
|MICHIGAN (D, Sen. Debbie Stabenow) (Last month: 13)
The Chinese ad and a real flirtation with birtherism makes us wonder whether former Rep. Pete Hoekstra really wants to be a senator. If he's the Republican nominee, Sen. Debbie Stabenow could almost use Hoekstra's own ads to attack him.
|HAWAII (Open D, Sen. Dan Akaka is retiring) (Last month: 16)
The daunting reality that former Gov. Linda Lingle would need to win a federal race with the help of as many as two in every five Obama voters has tempered some Republican hopes here. Still, Republicans have won in Hawaii when the Democratic primary turns ugly, so Lingle retains the hope that Rep. Mazie Hirono and ex-Rep. Ed Case blow up at each other.
|CONNECTICUT (Open I/D, Sen. Joe Lieberman is retiring) (Last month: 17)
A recent Quinnipiac poll shows positive ads Linda McMahon is running have improved her image. The downside is that it doesn't take much to remind voters about her career as a WWE executive. Rep. Chris Murphy is more of a favorite than his poll numbers suggest.
|PENNSYLVANIA (D, Sen. Bob Casey) (Last month: 18)
Congratulations to retired coal mining executive Tom Smith -- you've won the right to get smooshed by the popular Casey. Democrats at the national level may have a growing problem with working-class white voters, but this Son of Scranton sure doesn't.
|NEW JERSEY (D, Sen. Bob Menendez) (Last month: 20)
If Menendez represented a more ideologically balanced state, his low name identification and close association with Democratic machines that are constantly embroiled in some ethics violation or another would put him in real danger. But he lives in New Jersey, a state that hasn't elected a Republican to a Senate seat since 1972. State Sen. Joe Kyrillos is well-funded, but he's got an "R" after his name, which might as well be a scarlet letter in the Garden State.
|WEST VIRGINIA (D, Sen. Joe Manchin) (Last month: 19)
Sen. Joe Manchin may be the only Democrat in the country to actually bolster his own standing by refusing to endorse a president of his own party. Manchin is running like he's one point ahead, rather than the 20 or so point margin he's really winning with.