The six seats most likely to flip party control in our newest Fix rankings of the Senate are all currently controlled by Democrats -- a series of ratings that suggest Republicans are poised to pick up the six seats they need to retake control of the upper chamber in 25 days time.

Two Democratic open seats -- Montana and West Virginia -- seem like certain GOP pickups. South Dakota's open seat, meanwhile, still favors former governor Mike Rounds (R), but the Democratic Senatorial Campaign Committee's decision to pump $1 million into the state suggests they see a path, most likely with Democratic-friendly former GOP Sen. Larry Pressler, who is running as an independent.

The next three seats all feature Democratic incumbents -- Mark Pryor, Mary Landrieu and Mark Begich -- running in unfriendly states for their party. All three remain viable, but polling suggests that momentum in each of the races is with their Republican opponents, thanks in large part to the unpopularity of President Obama and the national Democratic Party.

FridayLine

Win those six seats, and Republicans have the majority. Unless, that is, they lose in Kansas -- a real possibility -- where independent Greg Orman and Sen. Pat Roberts (R) are locked in a tight race.

(It's not clear whom Orman would caucus with if he won. Some have reported that Orman would caucus with the majority party, but he hasn't really been that firm, and Republicans insist he won't side with them after they go after him these next few weeks.)

While GOP fortunes in Kansas and once-top-targeted North Carolina are looking surprising iffy, the movement of Colorado and Iowa in Republicans' favor over the last few weeks could even allow them to sustain losses in those unexpected places. Both Rep. Cory Gardner (R) in Colorado and state Sen. Joni Ernst (R) in Iowa have the momentum in their respective races, but Democrats remain optimistic that they can turn both back their way.

Once you get beyond the top nine races on our Friday Line, though, the pickings get slimmer. Yes, Sen. Kay Hagan (D-N.C) could lose, but her resiliency to date suggests she might not. Democrats still hold out hope that Kentucky and Georgia could be pickup opportunities -- and they might -- but neither are top-tier at this point.

Below are the 13 most competitive races in the country as of today. The most likely seat to switch is ranked No. 1.

To the line!

13. Kentucky (Republican-controlled): Democrats got real excited about an automated SurveyUSA poll last week showed Alison Lundergan Grimes (D) leading within the margin of error (by two points). Besides that poll, though, the last 11 public polls all showed Senate Minority Leader Mitch McConnell (R-Ky.) leading by between two and eight points. Meanwhile, Grimes’s awkward non-answer on whether she voted for President Obama is getting noticed – big time. (Previous ranking: 13)

12. New Hampshire (Democratic-controlled): Polls show Sen. Jeanne Shaheen (D) leads, but Republican former senator Scott Brown remains in striking distance. Republicans credit Brown's tireless effort on the campaign trail for keeping him in the mix. But Shaheen's made no major missteps. If that trend continues, there may be little Brown can do unseat her. (Previous ranking: 12)

11. Georgia (R): The political world is well aware of the likelihood of a runoff in Louisiana if, as expected, no candidate gets 50 percent plus one on Election Day. But it's also quite possible we could see a runoff in Georgia ... in January. Polling suggests businessman David Perdue (R) has a slight edge over Michelle Nunn (D), but he's not all that close to 50 percent. Nunn's best and probably only chance is to win is outright on Nov. 4; a Jan. 6 runoff electorate would likely favor Perdue no matter what happens nationally. It's worth noting that the last week has been a rocky one for Perdue, as documents emerged in which he said he "spent most of my career" outsourcing. (Previous ranking: 11)

10. North Carolina (D): Sen. Kay Hagan (D) continues to hold on to a small but steady lead in her race against state House Speaker Thom Tillis (R). (The last five polls released in the race all show her ahead by margins ranging from one to five points.) The problem for Tillis is that, unlike other Republican-leaning states hosting key Senate races this cycle, North Carolina hasn't turned into a straight referendum on President Obama. Instead, some of the controversial actions -- especially on education -- by the state legislature over the last few years have made it harder to keep the spotlight off of the Republican brand. It's now clear that Republicans could win the Senate majority and lose North Carolina -- a scenario that seemed pretty unlikely a year ago. (Previous ranking: 9)

9. Colorado (D): There was a moment in a debate this week in which you could practically see Sen. Mark Udall (D-Colo.) handing Rep. Cory Gardner (R-Colo.) a quote for an attack ad – talking about voting to cut Medicare Advantage. Gardner was already ascendant in the race, and is looking more like a favorite right now. Polls from Fox News and Quinnipiac in recent weeks have put Gardner up six and eight points, respectively. Suffolk University, meanwhile had Udall within a point. (Previous ranking: 10)

8. Iowa (D): Remember the days when there were doubts about whether Republican Joni Ernst could raise money? Those days are over. She hauled in $6 million in the third quarter, outraising Rep. Bruce Braley (D). Braley's saving grace may be well-funded Democratic cavalry that has come in to help him on the airwaves -- although even that may not be enough to overcome the image that he is out of touch with rural Iowans. He has no one to thank for that except himself after his infamous "farmer from Iowa" remark. (Previous ranking: 8)

7.  Kansas (R): CNN and Fox News polls this week, for the first time, didn't show Roberts trailing Orman. CNN had Roberts narrowly ahead (by one point), while Fox had him up five. This is still quite a worrisome race for Republicans though, and they're bringing out all the big guns for Roberts -- from Bob Dole to Mitt Romney to Sarah Palin to Jeb Bush to Rand Paul to Paul Ryan. You think this race is important? (Previous ranking: 7)

6. Alaska (D): Everyone agrees that Sen. Mark Begich (D) has run a serious and credible campaign. Everyone also agrees that Alaska is a very hard state for a Democrat -- any Democrat -- to win. And former state attorney general Dan Sullivan (our new profile of him here) has turned out to be a better-than-expected candidate. Polling suggests this is now Sullivan's race to lose, but polling in Alaska is notoriously difficult, and Democrats believe their ground game migh save Begich. They probably need it to to salvage their majority. (Previous ranking: 6)

5. Arkansas (D): Bill Clinton was in the state earlier this week to stump for Sen. Mark Pryor (D) and other Democrats. Every time Clinton comes home, he's received as political royalty. But is that enough to save Democrats in a state that has been trending increasingly Republican for years? If Rep. Tom Cotton (R) defeats Pryor and Asa Hutchinson (R) is elected governor -- two distinct possibilities -- the GOP takeover will effectively be complete. (Previous ranking: 5)

4. Louisiana (D): Sen. Mary Landrieu (D-La.) this week replaced her campaign manager. With less than four weeks until Election Day and about two months until a likely runoff date with Rep. Bill Cassidy (R-La.), that's not a good sign. But it's not a death knell, either. As Philip Bump reported this week, several folks have replaced their campaign managers this late in the game and still won. That said, few if any of them were as vulnerable as Landrieu. (Previous ranking: 4)

3. South Dakota (D): Well this one just got interesting. We're not moving South Dakota from the No. 3 spot on this list, but while it was looking like a done deal (ala Nos. 1 and 2) for Republicans before, it's looking a lot closer to No. 4 these days. A SurveyUSA poll showed former governor Mike Rounds (R) at 35 percent, former GOP senator Larry Pressler (I) at 32 percent and Democrat Rick Weiland at 28 percent. Rounds is taking on water and the Democratic Senatorial Campaign Committee just launched a $1 million ad campaign against him, apparently hoping either Pressler or Weiland can win. Pressler might be their best hope, but again, it's not clear with whom he would caucus. (Previous ranking: 3)

2. West Virginia (D): Secretary of State Natalie Tennant (D) has run a respectable race. But she was never going to beat Rep. Shelley Moore Capito (R), a very strong candidate in her own right, in a year that favors Republicans nationally in a state where Obama is persona non grata. (Previous ranking: 2)

1. Montana (D): After Kansas and South Dakota, we've learned to never say never when it comes to any race. But if you're looking for a sure bet, Montana is the closest thing you are going to find on the Senate map. There is no sign that Rep. Steve Daines (R) is headed for anything less than an easy win over Democratic state Rep. Amanda Curtis. (Previous ranking: 1)