GOP Rep. Martha McSally’s decision to enter the Arizona Senate race has opened up her hotly contested House seat, giving Democrats even more hope that they can win back the seat in 2018.

Republicans say they still have a chance at holding the 2nd District seat in southern Arizona, especially with the right candidate. But Democrats see energy on their side, fueled in part by a backlash to President Donald Trump. And they are hopeful the race will be an example of a Democrat flipping a seat that Hillary Clinton carried in November.

“The path to a Democratic majority in the House runs right through this district,” said former Democratic Rep. Ron Barber, who represented the district from 2012 to 2015.

Swing seat

Barber knows better than most how competitive the 2nd District can be. After winning a special election to fill the seat vacated by Democratic Rep. Gabrielle Giffords after she was shot at a constituent event, Barber won a full term in 2012, defeating McSally by just over 2,400 votes.

Barber, who was Giffords’ district director, then lost a rematch with McSally in 2014 by 167 votes.

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GOP Rep. Jim Kolbe had represented the area for two decades, but it has been more competitive since he retired, and Giffords won the open seat in 2006.

Now that the seat is once again open, Democrats believe they have an even greater chance of winning it back. The 2nd is one of 23 districts represented by a Republican that Clinton carried in November (she took it by 5 points). The district also includes 80 miles of the southern border with Mexico, and roughly 21 percent of eligible voters are Latino, according to the Pew Research Center.

One-third of registered voters in the district are Republican, one-third are registered Democrats and 30 percent are not affiliated with a party.

Republicans are hopeful a contested primary on the Democratic side could weaken the eventual nominee, but some GOP operatives in the Grand Canyon State worry about their chances without a strong fundraiser like McSally.

“That’s one of my biggest concerns,” said former state GOP Chairman Robert Graham when asked about holding on to the newly open seat.

Graham and other GOP operatives raised concerns about the top Democratic contender, former Rep. Ann Kirkpatrick, and her strong fundraising ability. Kirkpatrick previously represented the neighboring 1st District, and vacated her House seat to run unsuccessfully against GOP Sen. John McCain in 2016.

National outside groups are also eyeing the race for 2018.

The Congressional Leadership Fund, a super PAC aligned with House GOP leadership, had opened up an office in the district.

A CLF spokesperson said “all options are on the table” for their plans for the district now that it’s an open seat race, including getting involved in the Democratic primary. CLF has acknowledged it could play in Democratic primaries across the country to try and push weaker candidates through to the general election.

Primary battle

Before the general election, candidates have to survive a long primary season, with the election scheduled for Aug. 28.

On the Republican side, Lea Marquez Peterson is the lone candidate who has filed with the Federal Election Commission, and that’s by design.

She announced her candidacy even before McSally officially announced her Senate run to ward off potential primary candidates, according to a consultant with her campaign.

“The Democrats already had many months’ head start, and this is going to be a big, expensive congressional race,” the consultant said. “We wanted to put our marker down that she was interested.”

Marquez Peterson, who is known in the area as president of the Tucson Hispanic Chamber of Commerce, has also met with those reportedly considering jumping in the race and encouraged them not to run.

She could scare off even more challengers with her fundraising ability. Her campaign announced last week that she raised more than $215,000 in the first three weeks since declaring.

“It would be huge,” a national GOP strategist said about the prospect of an uncontested primary. “It would allow her to basically stockpile resources and build a campaign organization focused on taking out a Democrat while they completely deplete their own resources and divide themselves.”

The Marquez Peterson consultant said they were preparing to campaign against either Kirkpatrick or physician and former state legislator Matt Heinz, who is also running in the Democratic primary. A handful of other candidates have filed on the Democratic side as well.

Heinz was the 2016 nominee and lost to McSally by 14 points, and he hopes his name recognition built from the 2016 race will help him this year.

Kirkpatrick has so far outraised the primary competition. She raked in $400,000 in the most recent fundraising quarter, busting records for House challengers in Arizona, according to her campaign. The campaign announced she would enter 2018 with $465,000 in cash on hand.

Kirkpatrick has endorsements from Barber, who pushed her to run, and Giffords.

The primary is one of the few races where national Democrats have weighed in, with leaders such as House Minority Leader Nancy Pelosi and Minority Whip Steny H. Hoyer donating to Kirkpatrick’s campaign. The congresswoman was also included in the Democratic Congressional Campaign Committee’s Red to Blue Program for top challengers.

The Kirkpatrick campaign said the support from national Democrats would not be an issue in her race and was actually a reflection of her strength as a candidate.

“Ann has the experience winning tough races and getting things done in Congress,” said campaign spokesman Rodd McLeod. “She is effective and tough, which is why she has earned so much support from local and national elected officials and organizations.”

Heinz acknowledged in a phone interview that he won’t be able to match Kirkpatrick’s fundraising. But he said his strength in health care policy — he’s continuing to work at the Tucson Medical Center during the campaign — and his ties to the district are an asset.

Kirkpatrick recently moved to Tucson to be closer to her grandchildren, and Democrats shrugged off criticisms that she could be cast as a carpetbagger. They pointed out that Kirkpatrick attended law school in the district and worked for the Pima County Attorney’s Office early in her career.

Despite the crowded Democratic primary, even Rep. Raúl Grijalva, who endorsed former Assistant Army Secretary Mary Matiella in the 2nd District primary, said last month that Kirkpatrick was expected to win the Democratic nomination.

“I think it’s going to be a close race,” Grijalva said on “The Buckmaster Show.”