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CNN  — 

Democrats’ historic 2018 midterm gains should put them on the defensive this year, but with the national environment trending their way, they’ve got plenty of offensive opportunities that could help them hold or even expand their House majority in 2020.

In fact, half of the districts on CNN’s inaugural ranking of the top 10 House districts most likely to flip partisan control are GOP-held seats, including the top two. Many share similarities with the kinds of demographically changing and increasingly suburban districts where Republicans saw slippage in 2018. Meanwhile, many of the Democratic freshmen who flipped Trump districts in 2018 enjoy healthy cash advantages over their GOP opponents, while others failed to even attract competitive challengers.

The battle between President Donald Trump and Democratic nominee Joe Biden will loom large in these 10 races, so the presidential race, as well as past presidential performance, are important factors in the ranking. It’s no surprise that one of the few remaining seats Hillary Clinton carried in 2016 that is still represented by a Republican tops this list.

Six of the 10 districts on this list are open seats, where the incumbent is not running for reelection. Half of those are in Texas, which the Democratic Congressional Campaign Committee has called “ground zero” in its effort to expand the battlefield. And in two others – a GOP-held seat in New York and a Democratic-held one in Iowa – the lack of a longtime incumbent on the ballot makes it more likely those seats will flip.

House races are becoming more and more nationalized, but local dynamics and candidate quality still matter. That’s why two vulnerable incumbents who represent districts carried by the opposite party’s 2016 presidential nominee don’t make the top 10. Trump carried Minnesota Rep. Collin Peterson’s 7th District by about 30 points – more than any other district represented by a Democrat. There’s no question that Peterson, who narrowly defeated an underfunded challenger the past two cycles, is in for a tougher race against a Republican with national party backing this year.

But the chairman of the House Agriculture Committee, who voted against impeachment, is a known brand in this sprawling district. The same logic explains why New York Rep. John Katko, a Republican in a district Clinton carried by nearly 4 points, doesn’t make the list despite facing a repeat challenger who enjoys more national backing than she did two years ago. Those two races are still rated in the incumbents’ favor, according to Inside Elections with Nathan L. Gonzales, a CNN contributor.

Other Republican districts that may be shifting, either because voters have soured on Trump, demographics have changed or both – like Indiana’s 5th, Nebraska’s 2nd, Missouri’s 2nd or Ohio’s 1st – are worth keeping a close eye on in the months ahead. As is a newly-held Republican district in California that flipped parties earlier this year in a special election.

Lastly, two GOP-held districts in North Carolina that are likely to flip are not on this list because court-mandated redistricting made them much safer territory for Democrats.

Here are the top 10, which CNN will be updating ahead of the election:

Democrat Gina Ortiz Jones’ race against GOP Rep. Will Hurd was one of the closest elections of 2018. But now Hurd – the only Black Republican in the House – isn’t running for reelection, and Jones is once again trying to flip a district that Clinton carried by more than 3 points. A former Air Force intelligence officer, Jones has had the race to herself for most of the summer. She easily won her March primary, while the GOP contest wasn’t decided until late August, when Trump’s pick, former Navy cryptologist Tony Gonzales, emerged as the nominee after his runoff opponent dropped his recount effort. This expansive border district has been an elusive target for Democrats the past two cycles, but Jones – who had $3 million in the bank at the end of June to Gonzales’ $391,000 – has a strong profile and should benefit from presidential turnout in an increasingly competitive state.

This district outside of Atlanta was home to the closest House race in the country in 2018. Although it backed Trump by about 6 points, it’s representative of the increasingly affluent, well-educated and suburban areas that have soured on Trump and are moving in Democrats’ direction. That should boost Democrat Carolyn Bourdeaux, who came about 400 votes shy of defeating Republican Rep. Rob Woodall, who’s not seeking reelection. Bourdeaux, a public policy professor, had about $760,000 in the bank at the end of June compared to $106,000 for Republican Rich McCormick, a Marine veteran and emergency room doctor who had poured more than half a million dollars into his campaign. With Georgia becoming a battleground up and down the ballot, this will likely be an expensive race. McCormick’s embrace of Trump – especially on coronavirus – and backing from the political arm of the conservative House Freedom Caucus may not go over well if voters are looking to send a message to the President.

The fight between Democratic Rep. Xochitl Torres Small and Yvette Herrell is the only 2018 rematch on this list. The Democratic freshman won by less than 2 points in 2018 in a district Trump carried by 10 points. Trump still has support here, and Republicans argue that Herrell, who won a competitive primary earlier this year, is a stronger candidate than she was in 2018, plus her Democratic opponent now has a voting record. By the end of June, Herrell had raised more than double what she raised at the same time two years ago. But Torres Small still had a huge cash on hand advantage – $3.9 million to Herrell’s $379,000.

Democratic Rep. Kendra Horn’s upset victory over GOP Rep. Steve Russell was perhaps the biggest surprise of 2018 – and it immediately catapulted her to the top of most vulnerable lists heading into 2020. Trump carried the district by more than 13 points, and she now has a voting record that Republicans are using to tie her to the national party. She’s facing Republican state Sen. Stephanie Bice, who cut a more moderate image in the primary, talking about teachers and education in a way that could appeal to suburban women – a key demographic in this district. But after a late August runoff, Bice started the general election at a financial deficit with only $80,000 in the bank as of August 5, compared to $2.6 million for Horn by the end of June.

Democrats were a little relieved when Republicans’ top recruit for this district dropped out late last year. But Burgess Owen, a former NFL player and Fox News commentator who won a four-way primary, is giving Democratic freshman Rep. Ben McAdams a competitive race. Trump carried the district by nearly 7 points, and Owens – who spoke at the Republican National Convention last week – isn’t distancing himself much from the President, embracing his rhetoric about fighting socialism. But Utah has been less friendly to Trump than other red states, and the 4th District, unlike some other Trump districts that flipped in 2018, has a history of electing moderate Democrats like former Rep. Jim Matheson. McAdams, the former Salt Lake County mayor, had a $2.6 million war chest compared to about $90,000 for Owens at the end of June. But outside group spending may give Owens the help he needs to communicate.

An open-seat race in the Dallas suburbs is ripe opportunity for Democrats, whose candidate, Candace Valenzuela, would be the first Afro-Latina in Congress. Republican Rep. Kenny Marchant won this district by just 3 points in 2018, after winning it by nearly 17 points two years earlier – a sign that this Trump district was moving away from Republicans. Former Irving Mayor Beth Van Duyne is one of the record number of Republican women who have won nominations this year, and her profile may help win over some of the suburban women that Republicans have been losing. Valenzuela, a former school board member, had only $111,00 in the bank after her primary runoff, while Van Duyne, who avoided a runoff, had $483,000 at the end of June. But both women will benefit from plenty of outside spending.

Rep. Joe Cunningham flipped this Charleston-area district after GOP Rep. Mark Sanford – an outspoken Trump critic – lost his primary. But Republicans see state Rep. Nancy Mace, the first woman to graduate from the Citadel, as a stronger candidate than 2018 nominee Katie Arrington, who handed Cunningham a gift that kept on giving when she initially said she supported lifting a ban on offshore drilling. Cunningham used his opposition to drilling – an important issue in this coastal district – to pick off endorsements from GOP mayors, and he’s arguing he’s followed through on that promise, with the House passing his bill to ban offshore drilling last fall. But his time in DC is also being used against him, with Republicans trying to tie him to the national party to argue he’s out of step with a district that voted for Trump 13 points. Cunningham had $3.1 million in the bank to Mace’s $743,000 at the end of June.

This southeastern Iowa district is the rare Democratic-held seat that is in play this year because the incumbent, seven-term Rep. Dave Loebsack, is retiring. Trump carried the district by 4 points in 2016. Biden and Trump will battle for the Hawkeye State, while GOP Sen. Joni Ernst is on defense, as are two freshmen Democrats who flipped Trump districts in 2018. Of the three competitive Iowa seats, this one might be the toughest for Democrats to hold, with public polling bearing this out. Republican state Sen. Mariannette Miller-Meeks led former Democrat state Sen. Rita Hart 48% to 44% among likely voters in a Monmouth University survey from early August. (Democratic congresswomen led in polling of the other two competitive districts.) Miller-Meeks, an ophthalmologist and Army veteran, has lost three challenges to Loebsack, so she’s well-known here. Hart, the 2018 lieutenant governor nominee, still needs to introduce herself to more voters in the district. Hart ended June with about $1.4 million to $504,000 for her GOP opponent.

The story in this Long Island district is the reverse of the Iowa district above: Republican Rep. Peter King’s retirement is making this seat more competitive for Democrats. Democrat Jackie Gordon, a former Babylon councilwoman and veteran of the Army Reserves, had a significant cash advantage (about $1 million) over Republican state Assemblyman Andrew Garbarino, who ended June with only $104,000. Trump won this district by 9 points in 2016, but slippage in the suburbs could cost him the district in 2020. Even King, the longtime incumbent, saw his margin of victory narrow from 24 points in 2016 to just 6 points in 2018. But Republicans think a law-and-order message and efforts to tie all Democrats to “defund the police” will resonate here.

Democrat Sri Preston Kulkarni, a retired Foreign Service officer, is trying again to flip this district after coming about 5 points short two years ago against Republican Rep. Pete Olson, who’s not running for reelection. The Houston area-district backed Trump by 8 points in 2016, but the narrowing of Olson’s margin of victory in the midterms (he won by 19 points in 2016) underscores how diversifying suburban districts like this one may be moving away from Republicans. The DCCC ran its first-ever digital ads in Hindi and Chinese here. Republican Troy Nehls, an Army veteran and county sheriff, has a profile in the district and is running on a law-and-order message. He won a resounding primary victory but may have been bruised by negative attacks from a self-funding candidate that left him with just $30,000 to Kulkarni’s $1.2 million at the end of June.