There are two tiers on this list. There is near universal agreement that the first six Members aren't returning to Congress. Then there are the next four Members, all of whom are currently in Tossup races. Determining who belonged in the second group was tough. There are any number of Members who are about as vulnerable as the ones we listed. Among them: Reps. Jim Matheson (D-Utah), Brian Bilbray (R-Calif.) and Robert Dold (R-Ill.).
Almost everyone listed earned a spot here either because of redistricting or because of the 2010 GOP wave. It's no coincidence that four of the Members are freshmen in rematches from 2010 (although it's hard to count Rep. Charles Bass as a true freshman).
Our final list is ranked in order of vulnerability.
Richardson is the only Member on this list who faces a member of her own party - and a fellow Member - on the ballot. Her race against Rep. Janice Hahn, created by California's new "top-two" primary system, was mostly over before it began. The state party and powerful California Labor Federation are with Hahn. Throw in the persistent ethics trouble Richardson has found herself in since she came to Congress, including being officially reprimanded on the House floor in August, and the result is a Member who is all but certain to lose.
2. Roscoe Bartlett (R-Md.) 10th term (61 percent)
The 86-year-old Congressman's district underwent one of the biggest partisan conversions of any in the country as a result of redistricting. The bottom line is it was drawn to elect a Democrat, and it will in November: businessman John Delaney. If national Republicans or their aligned outside groups had seen evidence that this race was winnable, they might have reserved TV time. But none of them seems willing to gamble in the very expensive Washington, D.C., media market. Bartlett should have retired, as many expected him to do.
Kissell has been on all three Top 10 Vulnerable Member lists we've done this cycle. But with a month to go until Election Day, there is the best tangible proof yet that his chances of winning a third term are slim. National Democrats recently pulled their TV reservations in Kissell's district - a big sign the former teacher and textile worker is viewed as a political goner. To be clear, Kissell had little control over his predicament. GOP-led redistricting was meant to decimate Democrats in the Tar Heel State. Kissell would need a miracle to overcome the partisan slant of his new district.
Walsh would be ranked higher on this list except that national Republicans recently reserved TV time in the Democratic-leaning suburban Chicago district where he is running for re-election. That indicates they have seen - and believe - polling that shows Walsh might actually still be in the race against Democrat Tammy Duckworth. Still, it is more likely Walsh will not return to the 113th Congress. If he were to somehow pull out a victory, it would be almost as much of a surprise as his 2010 victory. Almost.
By most accounts, Rivera is someone capable of defying political odds. But if the freshman lawmaker, reportedly under investigation by the FBI, somehow pulls off his re-election, it will be beyond miraculous. Rivera has been under an ethical cloud since he entered Congress. The national party won't spend any money to help him against Democrat Joe Garcia, who is also a flawed candidate. How bad have things gotten? Last week, the Miami Herald ran a story naming the GOP candidates looking to try to win the seat back in 2014. The message was sent to Rivera: Good riddance.
Buerkle, like four other Republicans on this list, was swept into Congress by the strong GOP tide in 2010. Like most of her freshman colleagues listed here, she probably would not have won in a neutral political environment. Now she's attempting to win re-election in a district that will no doubt vote for President Barack Obama. That climb is steep enough. But she also faces the man she barely unseated in 2010: former Rep. Dan Maffei (D). Democrats insist that given the presidential turnout and voters' buyer's remorse, there's really no path to victory for Buerkle. However, the intensity of Buerkle's supporters is such that she could get a boost Election Day if it's close. But right now she looks to be a one-term wonder.
Benishek won in 2010 with a GOP wind at his back. He won't have that this year, but his bigger problem is that he hasn't ingratiated himself with voters during the past two years. Recent polls have shown Democrat Gary McDowell with a small edge but with a large number of undecided voters - not a promising sign for the incumbent. The race against McDowell is a rematch from 2010. While the district is conservative, it voted to send Democrat Bart Stupak to Congress for years. Right now, Benishek seems to be the slight underdog. But the race isn't over, yet.
8. Charles Bass (R-N.H.) 1st term (48 percent; previously served six terms)
Bass is a veteran of competitive races and the wave elections of 2006 and 2010 - the years he got swept out of and then back into Congress. This year there is no political tide moving in one direction and Bass' political skills will be tested in a neutral environment. His district favors Democrats, making him a top target from the very beginning of the cycle. He faces a rematch from 2010 with Ann McLane Kuster, who never stopped running after her loss two years ago. Much has been written about the demise of the New England Republican. Next month, Bass wants to prove the old Mark Twain adage true.
Barrow is the most battle-tested Member on this list. He has found ways to win in districts that he wasn't supposed to cycle after cycle. And he could still pull off a victory next month. What makes his task even more complicated this year is that he's running in a more Republican district - in a presidential year - than he has ever run in before. Barrow is good on the stump and is a pretty gifted retail politician. But he's got to convince more voters than ever to split their tickets. Republican Lee Anderson isn't regarded as a stellar recruit. But it might not matter.
10. John Tierney (D-Mass.) 8th term (57 percent)
Is the power of innuendo strong enough to end a long political career? For Tierney, the answer looks to be yes. The Congressman has been accused of no wrongdoing, but his proximity to his wife's family's trouble with the law over an offshore gambling ring has been politically toxic. He faces Republican Richard Tisei in a comfortably Democratic district. In a presidential year, Tisei will have to outperform GOP presidential nominee Mitt Romney by a big margin. But the wind's not at the incumbent's back, with recent polls showing Tisei ahead. Tierney could still win, but it will be ugly.
Rep. Elijah Cummings, D-Md., right, hugs Harold Schaitberger, General President of the International Association of Fire Fighters, after the Congressman spoke at the IAFF's Legislative Conference General Session at the Hyatt Regency on Capitol Hill, March 9, 2015. The day featured addresses by members of Congress and Vice President Joe Biden.