Rep. Tammy Duckworth (Ill.) is running for the U.S. Senate, giving Democrats a top recruit in a potentially competitive race that could determine control of the chamber. (Seth Perlman/AP)

Senate Democrats are well positioned in 2016 both in terms of the landscape — they are defending just 10 seats compared with 24 for Republicans — and the early-recruitment wars. So much so that it’s clear they have at least a shot at winning back the Senate majority in November 2016.

In places such as Illinois and Wisconsin, Republican incumbents start as, at best, even-money bets to win. And in the case of Illinois, the odds are probably slightly worse.

The key for Democratic chances at the majority lies in landing top-tier recruits such as Gov. Maggie Hassan in New Hampshire and former senator Kay Hagan in North Carolina. In Pennsylvania, where national Democrats have been clearly unhappy with the prospect of former congressman Joe Sestak as their nominee, keep an eye on Katie McGinty, the chief of staff for Gov. Tom Wolf (D).

Republicans have very few pickup chances and have yet to land solid recruits in their two best opportunities: Colorado and Nevada. There is optimism about Rep. Joe Heck running in Nevada, but the recent no-go decision by Rep. Mike Coffman in Colorado leaves Republicans without one of their best options to take on Sen. Michael Bennet (D).

The 10 Senate races below are considered the most likely to switch parties in 2016, with the No. 1 race the most likely flipper and all 10 races considered competitive.

10. Arizona (Republican-controlled): The decision of Rep. Ann Kirkpatrick (D) to run was a surprise to many. She seems to be gambling that a serious primary challenge to Sen. John McCain (R) in the form of Rep. Matt Salmon could produce enough chaos for her to win in what is a GOP-leaning state. Maybe. And Salmon’s not in the race yet.

9. North Carolina (R): Hagan seems decidedly noncommittal about running again — with no date set for her to make up her mind. And it’s not entirely clear how vulnerable Sen. Richard Burr (R) is even if she does make the race.

8. Ohio (R): Democrats are optimistic about their chances here because polling shows former governor Ted Strickland (D) ahead of Sen. Rob Portman (R). Republicans insist that Strickland is at his high-water mark — that his lead is all about name recognition from his time as governor. I tend to think they’re right. The top-of-the-ticket dynamic in what has been one of the swing states in the past four presidential elections could tilt a close race.

7. Colorado (Democratic-controlled): This seat gets tougher for Republicans because of Coffman’s decision not to run. Republicans point out that Sen. Cory Gardner (R) opted against the 2014 race and then reconsidered, but we’ll believe it when we see it. And Gardner was the shining star of the Colorado Republican Party in a way that Coffman just isn’t. The GOP bench in the state is also surprisingly thin.

6. New Hampshire (R): Does Hassan run? Or not? We’ll find out later this summer when the state legislative session ends. If she passes, there’s not an obvious second choice for Democrats. If Sen. Kelly Ayotte (R) escapes that tough race, expect her to be mentioned as a possible Republican vice presidential pick next year.

5. Pennsylvania (R): Montgomery County Commissioner Josh Shapiro’s decision not to run is a setback for the anti-Sestak crowd. But it’s clear that Democrats are committed to finding someone other than Sestak as the challenger to Sen. Pat Toomey (R). Despite being in a blue-leaning state, Toomey is a very able candidate, as he proved in 2010, and won’t go down without a well-organized and well-executed challenge.

4. Nevada (D): The big question here is whether Republicans can persuade Heck to run for the open seat of retiring Senate Minority Leader Harry Reid (D-Nev.). It looks as if Heck is leaning toward the race, but history is a reminder that until a candidate says he’s in, he’s not in. Democrats have quickly coalesced behind former state attorney general Catherine Cortez Masto as their pick.

3. Florida (R): Democrats would be feeling even better here if it weren’t for these two words: Alan Grayson. The controversial (to say the least) liberal congressman continues to talk a big game about challenging Rep. Patrick Murphy in the Democratic primary. That would be a problem for the moderate-leaning Murphy and national Democrats — and conservative groups know it. Republicans have their own primary shaping up between tea party-backed Rep. Ron DeSantis and establishment choice Carlos Lopez-Cantera, the lieutenant governor.

2. Wisconsin (R): Sen. Ron Johnson (R) continues to make headlines — for the wrong reasons. The latest was his defense of “Lord Business,” the bad guy in the “LEGO Movie.” Um, okay. Democrats have placed lots of faith in former senator Russ Feingold, which is somewhat interesting, given how terrible a campaign he ran in 2010 against Johnson. Still, this is a prime pickup opportunity for Democrats, as early polls show Feingold with a healthy lead.

1. Illinois (R): Hillary Clinton is almost certain to carry Illinois by double digits in 2016. Can Sen. Mark Kirk outperform the top of the Republican ticket by that kind of margin? Anything’s possible, but it’s a very hard race — particularly because Democrats landed their first-choice recruit in Rep. Tammy Duckworth. Duckworth doesn’t have a clear path in the primary, though.