With the House GOP on defense in a difficult national environment, the 10 most vulnerable incumbents six months out from Election Day are all Republicans.

Republicans have pickup opportunities in November, but this is a ranking of the incumbents most likely to lose, not of seats most likely to flip — so there are no open seats on the list.

The biggest change from when we last compiled the list, a year out from Election Day? The most vulnerable member, California Rep. Darrell Issa, is retiring, sliding Iowa Rep. Rod Blum into the top spot. Blum was near the top of the list for most of 2016 — and then he won. But both Republicans and Democrats agree he’s in trouble this year.

Virginia Rep. Barbara Comstock also moves up the list, while Colorado Rep. Mike Coffman, Florida Rep. Carlos Curbelo and California Rep. Steve Knight make the cut this time in part because of the difficulty of holding their districts, all of which Hillary Clinton carried. Pennsylvania Rep. Keith Rothfus makes his debut here, thanks to redistricting.

Watch: Iowa’s Blum Now Most Vulnerable House Member, Nelson Moves Up List for Senate

Some familiar names shifted around. New York Rep. John J. Faso Jr. slid from third to fifth, while Minnesota Rep. Jason Lewis fell from second to fourth. New York Rep. Claudia Tenney moved up from seventh to sixth.

As always, this list is compiled after consultation with strategists from both sides of the aisle and the race ratings from Inside Elections with Nathan L. Gonzales.

Blum’s district is the type of seat Democrats want back in their column. (Voters here backed Trump, but Obama carried it twice by double digits). Democrats think they have the right candidate. State Rep. Abby Finkenauer still has to win the primary, but she is already up on TV with an ad featuring her dad, a retired pipe fitter. Finkenauer outraised Blum in the first quarter of the year by $180,000, but the incumbent still has a cash on hand advantage. Blum could also be dogged by a report that he violated House Ethics rules. He did not disclose that he owned a marketing company, The Associated Press reported. Blum said it was an “administrative oversight.”

Even as one of the GOP’s stronger incumbents (she over-performed Trump by double digits last cycle), Comstock moves up on the list because of the district she’s in and the national environment. She’s broken with her party on some votes that would have hurt federal workers in her district, and she clashed with Trump (on camera) earlier this year when she told him, “We don’t need a government shutdown.” She voted against the GOP health care plan. But on other issues, such as the GOP tax overhaul, she’s stuck with leadership. That could be a vulnerability in an affluent district where many voters claim state and local tax deductions. Comstock starts with a hefty financial advantage, while Democrats still have a crowded primary to get through. But all of the top contenders have resources and the national party will make sure the nominee is well-equipped heading into the fall.

If not for a new congressional map, Rothfus wouldn’t be on this list. But the state Supreme Court imposed new district lines for 2018, and his district in southwestern Pennsylvania shifted from one Trump carried with 59 percent of the vote, to a seat Trump would have taken by 2 points with 49 percent. Rothfus represents around half of the new district. His tough spot is made even more difficult with newly elected Democratic Rep. Conor Lamb challenging him under the new lines. Lamb will benefit from a sizable war chest and high name recognition from the hotly contested March special election in a neighboring district that garnered immense media attention. He has $1.7 million in the bank, slightly more than Rothfus’ $1.6 million.

Lewis moves down a few spots but remains vulnerable in a rematch with Democrat Angie Craig. Besides a more favorable national environment, Craig’s biggest advantage this year may be that the same third-party candidate who cut into her margin last year isn’t running. Lewis is by no means the flamethrower in Congress that his radio talk show past would have suggested. But Democrats see plenty to attack him on, starting with his vote to repeal the 2010 health care law. Lewis ended the first quarter with slightly more money in the bank than Craig.

Faso is still looking vulnerable, even though it’s not clear whom he will face in November. Even though Trump carried this upstate New York district, Democrats view it as a target since it voted for Obama twice. Democrats are confident a strong contender will emerge from the crowded primary. Five of the seven challengers have more than $400,000 in the bank. Lawyer Antonio Delgado had more cash on hand than Faso. Some Republicans note the Democrats may be pushed too far to the left in the primary (which has started to happen on issues such as gun violence). Faso’s broken with his party and voted against the tax overhaul, but his vote for the GOP health care bill is still expected to be a major issue in the general election.

Some Republicans note that part of Tenney’s vulnerability is self-inflicted, pointing to controversial statements like saying mass murderers “often end up being Democrats.” Trump carried the 22nd District by double digits, but Tenney won her first term by a narrower 6-point margin in a race with a third party candidate. Tenney is now facing a well-funded challenger in state Assemblyman Anthony Brindisi, who has more cash on hand. House Majority PAC, a Democratic super PAC, is already on the airwaves, attacking Tenney for supporting the GOP health care bill. Tenney said she has been outraised before and brushed off the controversial remarks by saying she is in line with her district.

The South Florida congressman is making the list for the first time this cycle, in large part because of the blueness of his district and his surprising vote to repeal the 2010 health care law. He generally isn’t afraid to buck his party, whether taking a stand on climate change or dropping the word “impeachment” in regard to the president. It remains to be seen how strong Democrat Debbie Mucarsel-Powell is at the congressional level (she lost a state Senate race in 2016). Curbelo started with a cash advantage and he vastly over-performed Trump in 2016, even if it was by defeating a flawed former congressman.

With retirements opening up the list, Knight is a new addition. A former state legislator, he was re-elected to a second term in 2016 by 6 points, besting lawyer Bryan Caforio. Knight is now on the NRCC’s Patriot Program. Caforio is running again, along with Democrats Katie Hill, who runs a nonprofit, and volcanologist Jess Phoenix. Democrats see both Caforio and Hill as strong challengers, and both have more than $500,000 on hand. Knight has $1 million in the bank. Hill did outraise Knight in the first quarter of the year, bringing in $421,000 to his $347,000.

It’s possible Rohrabacher might not face a Democrat in November, but he still looks vulnerable in this Clinton district. He’s up against formidable opponents from both parties. Former Orange County GOP chairman Scott Baugh’s entrance into the race made it possible that two Republicans could advance to the general. Under California’s system, the top two vote-getters advance regardless of party. On the Democratic side, both businessman Harley Rouda and stem cell researcher Hans Keirstead have launched viable challenges. This district could also be one of the few where an investigation into Russian involvement in the 2016 election could actually have an impact. Rohrabacher has been known for his pro-Russia stances and ties to Vladimir Putin, and it remains to be seen whether that could hurt him should Russian meddling continue to make headlines.

Republicans believe Coffman is one of their strongest incumbents since he’s weathered tough races before. Like Comstock, his district’s makeup and a national environment favoring Democrats make him vulnerable. And this cycle, Democrats believe they have a strong challenger in Iraq War veteran Jason Crow (despite some headlines about the national party’s involvement in the primary). Coffman has a reputation as a tireless campaigner, so the question for him is whether the national environment will overwhelm his personal brand.

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