The Elizabeth Warren and Scott Brown race was bound to get nasty — it just took longer than expected. | AP Photos No lock on Senate races

Five weeks from Election Day, both parties jousting for control of the Senate face a stark fact: Neither has yet locked down races that should have been put away by now.

That means the Senate map has gotten bigger, not smaller, leaving races from New England to the Upper Plains to the Southwest all in play. Both parties will have to start making cutthroat decisions on money: Some candidates are going to get cut loose, and others will see a surge of cash.


Democrats are stuck with a continued slog in Massachusetts, where the only post-debate poll in the deep-blue Bay State show Elizabeth Warren and Sen. Scott Brown in a tie. They’re fending off a ferocious challenge by Linda McMahon in Connecticut while quietly hoping independent Angus King can stave off an onslaught of GOP attacks in a tricky three-way race that’s looking less like a sure thing every day.

Republicans have their own problems: They’re not cruising to victory in Montana and North Dakota, and there’s a palpable sense they’re on the verge of a major upset in Indiana, where state Treasurer Richard Mourdock has fallen slightly behind Democratic Rep. Joe Donnelly. Failing to retain the ruby-red Hoosier State would essentially destroy any shot at a GOP Senate majority.

With such a volatile, fluid Senate map entering October, POLITICO’s monthly list of the Senate’s ten most competitive races could easily be a list of 12 — of all the key seats, only Nebraska seems safely in Republican hands.

For Republicans to convert the four seats required to capture control, they’ll need to run the table in their dead-even red-state contests while defying presidential headwinds in Massachusetts and Nevada.

After a month of volatility, here are the latest rankings:

1. Massachusetts (up 1 spot)

It was bound to get nasty — it just took longer than expected. Brown has shifted the campaign to focus on Warren’s character, reigniting questions about her claim of Indian heritage and resurrecting her work defending an insurance company in an asbestos lawsuit. The searing message against the populist liberal heroine: She’s a phony. Warren stayed poised in their first debate, letting the barbs roll off her shoulders without a hint of indignation. But with third-party groups increasingly creeping into the race by phone and mail, the vitriol is only expected to escalate.

( PHOTOS: Massachusetts Senate race)

Who won September: Warren

Latest poll: Warren 43 percent, Brown 38 percent (Boston Globe/University of New Hampshire, 502 likely voters, Sept. 21-27)

2. Montana (up 1 spot)

The partisan divide in Montana is one of the sharpest that Mason-Dixon pollster Brad Coker has ever seen.

( Also on POLITICO: Tester rocks with Pearl Jam)

And the tension has boiled over, with GOP Rep. Denny Rehberg appearing to flip the bird to a Democratic tracker and Sen. Jon Tester calling Karl Rove a “son of a bitch.” The negativity has taken a toll on both candidates’ approval ratings. Tester is running as close to a pitch-perfect race as possible, but even Democrats acknowledge he could still lose because of the GOP registration and intensity.

Who won September: Rehberg

Latest poll: Rehberg 48 percent, Tester 45 percent (Mason-Dixon Polling, 625 likely voters, Sept. 17-19)

3. Virginia (down 2 spots)

The illustrious Tim Kaine-George Allen race falls to the third slot for the first time in 21 months of rankings. Kaine, former Democratic National Committee chairman, carved out a lead in five consecutive September polls and fought to ties in two others. He wasn’t perfect — an admission that he’d be open to an income tax on all Americans during a debate handed Allen a new cleaver to bludgeon him with. But it appears the bipartisan notes Kaine has been playing for months are beginning to bear fruit with swing voters, and the gender gap with women is widening. September is the first month the Kaine campaign has been up on television and as a result, they’ve moved the needle.

Who won September: Kaine

Latest poll: Kaine 44 percent, Allen 44 percent (Suffolk University, 600 likely voters, Sept. 24-26)

4. Nevada (up 2 spots)

In their first debate Thursday, Republican Sen. Dean Heller emerged the slight victor over Rep. Shelley Berkley, exhibiting a smoother presence and landing more specific jabs. At one point ahead of her closing statement, Berkley seemed seconds away from having her own Jan Brewer moment — pausing for several awkward seconds while she gathered her thoughts. Democrats continue to chest-beat about their registration advantage in Nevada and contend the early vote will soon reveal evidence of a Berkley surge.

Who won September: Heller

Latest poll: Heller 49 percent, Berkley 43 percent (NBC/Wall Street Journal/Marist, 984 likely voters, Sept. 23-25)

5. Indiana (new)

Mourdock hasn’t made the level of gaffes of a Sharron Angle, Christine O’Donnell or even Todd Akin. Yet the polls indicate Hoosier voters just haven’t warmed to the idea of giving him Sen. Dick Lugar’s seat. Put aside the hair-raising Howey Politics Indiana head-to-head result showing him behind Donnelly. More troubling to GOP operatives is that just 26 percent of Indianans view him favorably and that Donnelly performs better among independents. There’s a reason National Republican Senatorial Committee Chairman John Cornyn felt the need to swoop into the state: If Democrats flip the seat, it will be the story of the cycle and a stain on the Texas senator.

Who won September: Donnelly

Latest poll: Donnelly 40 percent, Mourdock 38 percent (Howey/DePauw University, 800 likely voters, Sept. 19-23)

6. North Dakota (down 2 spots)

On the same day Democrats leaked an internal poll showing Heidi Heitkamp up 4 points, Republicans emerged from the field with data shared with POLITICO showing the race breaking in Rep. Rick Berg’s direction by a couple of points. The tone of Heitkamp’s ads have hardened as she attempts to tag him as a shoddy property manager. Yes, there’s widespread agreement Heitkamp’s ads are better, but that’s not something voters usually pay attention to. Watch for the immensely popular Sen. John Hoeven to emerge late to help pull Berg across the finish line.

Who won September: Draw

No recent public polling

7. Wisconsin (up 1 spot)

Tommy Thompson had a rough and tumble month, falling behind Democratic Rep. Tammy Baldwin after being battered on the airwaves. Democrats did an effective job damaging his good-guy image and are emboldened by reshaping a race many were eager to write off for the GOP. Now that Thompson is receiving air cover by outside groups and is up with his own round of bare-knuckle ads, his team expects a rebound. His energized debate performance Friday night signaled he knows he has a fight on his hands.

Who won September: Baldwin

Latest poll: Baldwin 49 percent, Thompson 45 percent (Public Policy Polling, 842 likely voters, Sept. 18-19)

8. Connecticut (up 2 spots)

Rep. Chris Murphy has begun to dig out of the hole he was in last month, when Linda McMahon was pummeling him as an “ineffective career politician.” Two public surveys show the congressman with narrow single-digit leads, but Democrats know they are not out of the woods yet. The irony is that McMahon is actually winning independents, yet she’s losing about 20 percent of Republicans and needs her GOP base to come home if she’s going to win.

Who won September: Murphy

Latest poll: Murphy 48 percent, McMahon 42 percent (Public Policy Polling, 801 likely voters, Sept. 24-26)

9. Missouri (unchanged)

Rep. Todd Akin’s only real shot at resuscitating his beleaguered campaign was to drive a fiercely disciplined fiscal message and make no mistakes. Then he chastised Democratic Sen. Claire McCaskill for not being “ladylike.” Amazingly, Akin was losing women by only 7 percentage points in a Missouri Scout survey of the race. He deserves political points for calling the bluff of many of his own party who are now slowly and quietly lending their support after trumpeting calls for him to drop his bid. But make no mistake, the Dresden-style bombardment of the St. Louis congressman has only begun.

Who won September: Akin

Latest poll: Akin 48 percent, McCaskill 47 percent (MoScout/Chilenski Strategies, 817 respondents, Sept. 20)

10. Maine (new)

The September rankings drop both Ohio and Florida from the list to make room for the Pine Tree State, where Republicans are doubling down on Secretary of State Charlie Summers. As the Cook Political Report’s Jennifer Duffy noted, the party wouldn’t be investing so many resources if they weren’t seeing real erosion of independent Angus King’s lead.

It’s alarming enough that the Democratic Senatorial Campaign Committee is now being forced to invest money to beat up on Summers without boosting Democrat Cynthia Dill. Look for Summers to post fundraising numbers that will turn heads.

Who won September: Summers

Latest poll: King 45 percent, Summers 33 percent, Dill 14 percent (Rasmussen Reports, 500 likely voters, Sept. 25)