Senate candidates are debating one another with increasing frequency as Election Day nears, giving voters more chances to compare their options alongside one another. While the debates have proven unique opportunities for candidates to pitch their politics, policies, and personalities, the set-tos haven't dramatically shifted momentum to one side or the other. 

To explore why, let’s start in Massachusetts, home to the cycle’s highest-profile Senate race. Sen. Scott Brown (R) and Elizabeth Warren (D) have debated three times and will meet once more on Oct. 30. Polling shows that most voters are tuning in. But neither Brown nor Warren has decisively used the debates to their advantage. 

(Elise Amendola/AP)

More than six-in-ten (61 percent) of those likeliest to vote had seen or heard at least one of the first two debates, according Western New England University survey conducted late last month and early this month. Among those voters, about as many said they were more likely to vote for Brown (30 percent) as for Warren (31 percent), based on the debate they most recently saw or heard. Thirty-seven percent said the debate didn’t make a difference.

While the first two Brown-Warren sessions were filled with heated exchanges and one-liners, neither candidate committed a huge gaffe; nor did either candidate dominate the other. So it’s not difficult to see why the first couple of meetings turned out as draws.

But even another debate in which there was a memorable misstep wasn't an end-all-be-all campaign moment.

In Virginia, former Democratic National Committee chairman Tim Kaine stole the spotlight at his Sept. 20 debate against former senator George Allen (R), but not the way his campaign wanted to see him do it. Kaine’s remark that he would be open to “some minimum tax level for everyone” forced a post-debate explanation and became fodder for an Allen attack ad five days later.

On its own, the debate hasn’t appeared enough to propel Allen into the lead, however. The Virginia race remains close – and has been all cycle – with most polls after the Sept. 20 meeting showing Kaine leading Allen by single digits.

On Thursday, Senate candidates debated in Nevada, New Mexico and Connecticut (The Hotline rounds up the coverage here). There were no real earth-shattering moments at any of the three. 

At the presidential level, Mitt Romney's debate performance last week was widely praised, and Republicans moved quickly to cast the campaign anew in the days that followed. Democrats, meanwhile, were forced to explain the president's performance. That's not something we're likely to see at the Senate level, even after debates as one-sided as the first Romney-Obama meeting.

Why? For one thing, presidential debates simply attract more attention and generate more media coverage. The pomp and circumstance not to mention the audience surrounding a presidential debate could never be matched at the Senate level.

The constant, from-all-angles post-game dissection that tends to shape the aftermath of presidential debate simply isn’t often found in state races. Local networks and papers cover the Senate debates, often with great breadth and depth, but it’s a matter of 10 stories versus hundreds; two or three minutes in a local news broadcast versus days worth of national coverage on cable.

All that said, statewide debates shouldn't be dismissed as mere background noise in Senate landscape. Warren and Brown have drawn some clear contrasts between one another on policy and personality. In Wednesday night's debate between Rep. Jeff Flake (R-Ariz.) and former surgeon general Richard Carmona (D), the candidates made some actual news -- Carmona on health care and Flake on signing pledges.

Benign as most statewide debates are, each one carries the risk of blowing up into a national story. Case in point: Arizona Gov. Jan Brewer’s (R) (extended) awkward silence at a 2010 debate.

And now, to our rankings of the 10 Senate seats most likely to change parties in 25 days. As always, these races are rated from most likely to flip — No. 1 — to least likely — No. 10.)

To the Line!

10. Connecticut (Democratic-controlled): The latest Quinnipiac poll showed Republican Linda McMahon and Rep. Chris Murphy (D) running about even. The Democratic Senatorial Campaign Committee's air offensive has had time to marinate since we last ranked the Senate races, underscoring the competitiveness of this race. At the same time, it's bad news for McMahon that she has to contend against a new foe on the airwaves. To be clear, this race remains a climb for Republicans (Obama led Romney by 12 points in the Quinnipiac poll, meaning McMahon might have to outrun the top of the ticket by 15 points) but its not settled yet. (Previous ranking: 10)

9. Indiana (Republican-controlled): Rep. Joe Donnelly (D) has done exactly what national Democrats have asked for -- keep this contest within range for the final stretch run. A bipartisan survey released last last month showed the race is about even, and Mourdock's partisan posture during the primary isn't helping him these days. Right now, he could use a hand from the man he defeated -- Sen. Richard Lugar (R). But he's not going to get one, since Lugar's shut the door on the possibility of stumping with his onetime opponent. (Previous ranking: 9)

8. Nevada (R): A Suffolk University poll released Thursday showed Sen. Dean Heller (R) with a small lead over Rep. Shelley Berkley (D). Overall, this race remains very tight. Can Heller run ahead of Romney in Nevada? That's the question for Republicans, as the Suffolk poll showed the Republican presidential nominee trailing Obama by a slim margin. (Previous ranking: 8)

7. Virginia (D): Despite Kaine's rough debate against Allen on Sept. 20, most recent polls show the Democrat with a single-digit lead over Allen. Two different polls released Thursday told two different stories, but Kaine can't be disappointed about his showing in either. (Previous ranking: 6)

6. Wisconsin (D): Democrats really took advantage of the three weeks after the mid-August primary, which left onetime frontrunning former governor Tommy Thompson (R) bruised and in need of financial reinforcements. They pounced on the airwaves, boosting Rep. Tammy Baldwin (D) against the well-known Republican. Now, the race looks about even with 3 and a half weeks to go. (Previous ranking: 5)

5. Massachusetts (R): Warren was largely on offense at Wednesday night's debate. More notably, neither Brown nor the moderator raised the issue of her Native American heritage, which could be fading as a focal point in the contest, at least for now. Both candidates have begun attacking each other over the airwaves in earnest, and the net result has been polls that have mainly showed Warren with a slight advantage. (Previous ranking: 7)

4. Montana (D): Could a race be more even? All cycle long, poll after poll has showed Sen. Jon Tester (D) and Rep. Denny Rehberg (R) in a tie. Tester is facing tougher odds compared to other Class of 2006 Democrats, like Sens. Claire McCaskill (Mo.) and Sherrod Brown (Ohio), but he's hanging tough in a state where Romney is the odds-on favorite at the top of the ballot. (Previous ranking: 4)

3. North Dakota (D): Mason-Dixon found this race to be deadlocked at 47 percent earlier this month. Heidi Heitkamp (D) has proven to be a more than capable contender against Rep. Rick Berg (R) in this increasingly Republican state. National Republicans' move to reinforce the effort in North Dakota late in the summer underscores how crucial a pickup opportunity this is for the GOP in the race for the majority. (Previous ranking: 3)

2. Maine (R): Since our last round of rankings, the Senate Democratic campaign arm has joined its GOP counterpart on the airwaves in this race. First, Republicans slammed frontrunning independent former governor Angus King. Then, Democrats responded to ding Republican nominee Charlie Summers. The real question here might be how much support Democrat Cynthia Dill can get (and how much Republicans will try to elevate her down the stretch). King is still in the driver's seat here, but his ride has grown bumpier. The increased national money this race has received has prompted us to move this from No.1 to No. 2. (Previous ranking: 1)

1. Nebraska (D): Let the speculation commence about what type of senator Deb Fischer (R) will be. Democrats' recruitment of Bob Kerrey was the best they could have hoped for when Sen. Ben Nelson (D) announced his retirement. But the former governor and senator has been no match for Fischer in this red state. (Previous ranking: 2)