The pieces are beginning to fall into place in the 2014 Senate landscape. But both parties still face some outstanding recruiting questions that will determine how much each side can expand the map. And the key to answering two of the biggest ones will lie in whether would-be candidates are willing to give up a lot to run. To wit:

* In Kentucky, Democrats are still waiting to see if Secretary of State Allison Lundergan Grimes (D) will challenge Senate Minority Leader Mitch McConnell (R). She wouldn't set a timetable when asked about it this week, and is no sure bet to run. Her allies note that she may opt to run for governor or attorney general instead. Grimes has strong potential to move up in the state, but if she doesn't choose wisely, her stock will suffer. And a Senate run against a well-funded opponent is a risky play.

Rep. Mike Rogers (R-Mich.) Rep. Mike Rogers (R-Mich.) (Jacquelyn Martin/AP)

* In Michigan, Rep. Mike Rogers (R) remains a possibility, but the latest signs are that he won't take the plunge. (Among other signs, his brother doesn't think he's going to run.) And who can blame him? Rogers would be giving up an awful lot as chairman of the House Intelligence Committee to run in a Democratic State against Rep. Gary Peters (D).

These are far from the only recruiting questions. (We delve into the rest of the big ones below.) But the two serve as reminders that as eager as many pols may be to run for the Senate, for some, it's not always the hottest ticket in town.


And now, to our list of the 10 Senate seats most likely to change control in 2014. As always, No. 1 is most likely to change control.

To the line!

10. (tie) Georgia (Republican-held) and Michigan (Democratic-held): Recruiting is the big question mark in both of these races. If Michelle Nunn runs in Georgia, Democrats will have a credible contender waiting in the wings in case Republicans nominate a flawed general election candidate like Rep. Paul Broun. And in Michigan, former secretary of state Terri Lynn Land is in. But Rogers would be a strong candidate for the GOP. (Previous rankings: 10)

9. Kentucky (R): For Grimes, it's not the Senate race or bust, as she could run for another statewide office. But for Senate Democrats eyeing a Kentucky pickup, it appears to be Grimes or bust. If she passes on this race, it would be a major victory for McConnell. And given all the talk at the outset of the cycle about the Republican leader facing potentially tough primary and general election challenges, it would be a pleasant surprise for Senate Republicans. (Previous ranking: 9)

8. Iowa (D): Sen. Tom Harkin’s (D) retirement made this into a battleground. But while Democrats had lined up their candidate-in-waiting (Rep. Bruce Braley), a series of Republicans have passed on the race, from Reps. Tom Latham and Steve King to Lt. Gov. Kim Reynolds and Agriculture Secretary Bill Northey. Now, they’ve got a primary featuring political unknowns, including former U.S. attorney Matt Whitaker and David Young, Sen. Chuck Grassley’s (R-Iowa) longtime chief of staff. (Previous ranking: 8)

7. Montana (D): Democrats are waiting to see whether former governor Brian Schweitzer, who just took a job as chairman of the board of the Stillwater Mining Co., will jump in. Before shareholders elected him to the board, he said his Senate decision would be based in part on what happened with the mining company. But he did not say which way it would drive him, and he has offered no hints about his plans since. If he runs, Democrats are favored to hold the seat being left open by retiring Sen. Max Baucus. If he doesn't, Republicans have the edge, although a major name has yet to get in the race. (Previous ranking: 7)

6. North Carolina (D): Republicans got their first somewhat-big-name Republican in this race when state House Speaker Thom Tillis jumped in last week. Now the question is how much primary opposition he’ll face. We’re still waiting on state Senate President Phil Berger and Rep. Renee Ellmers, among others. Sen. Kay Hagan (D) leads all of them in current polling, but that owes largely to the fact that none of them are well-known statewide. (Previous ranking: 6)

5. Louisiana (D): The scandals plaguing the White House could also cause headaches for Sen. Mary Landrieu (D), whose vulnerability rises and falls with national Republican prospects. But a Republican primary is shaping up, with the Senate Conservatives Fund considering supporting retired Air Force Col. Rob Maness against Rep. Bill Cassidy. Congressional Republicans are holding a fundraiser for Cassidy, but even the sponsors say it doesn’t mean they all support his bid. (Previous ranking: 5)

4. Alaska (D): The news that disastrous 2010 nominee Joe Miller has filed papers for a second bid made Democrats giddy. Indeed, it's not good news for Republicans. But it's difficult at this stage to see Miller catching lightning twice. Lt. Gov. Mead Treadwell, who would be a solid choice for the GOP, is exploring a bid. And if he is the nominee, Sen. Mark Begich (D) will have his hands full. (Previous ranking: 4)

3. Arkansas (D): No other incumbent is taking as much early heat over the airwaves as Sen. Mark Pryor (D). And he's getting it from both sides. New York City Mayor Michael Bloomberg's group is hitting Pryor on gun control from the left, while conservative groups are hitting him from the right. The Arkansas Democrat is the most vulnerable incumbent on the map right now. And if freshman Rep. Tom Cotton (R), decides to run, his outlook will be even dimmer. (Previous ranking: 3)

2. West Virginia (D): Democrats continue to come up snake eyes in the Mountaineer State, with two more candidates – attorneys Ralph Baxter and Nick Preservati – opting not to run against Rep. Shelley Moore Capito (R). Preservati’s exit is especially notable, given that he was looking more and more like “the guy” for Democrats. This race actually looks better for Republicans than it did last time, but it drops to No. 2 because, unlike in South Dakota, Democrats at least still have a shot at a well-known candidate. Secretary of State Natalie Tennant and state Supreme Court Justice Robin Davis still haven’t said no. (Previous ranking: 1)

1. South Dakota (D): Bad news for Democrats here: Former congresswoman Stephanie Herseth Sandlin is not running. U.S. Attorney Brendan Johnson, the son of retiring Sen. Tim Johnson, has indicated that he won’t run either. That leaves former Tom Daschle aide Rick Weiland as the only Democrat in the race for now, although party insiders skeptical of his chances have a year to cast around for another candidate. One thing that gives Democrats hope – former governor Mike Rounds might face a contentious primary as Rep. Kristi Noem considers taking him on from the right. (Previous ranking: 2)