For the first time in nearly 15 years, Republicans in Pennsylvania’s 18th Congressional District could lose their grip on the seat.

On its face, Tuesday’s special congressional election in the southwest corner of Pennsylvania should be a breeze for the GOP. The Cook Political Report rates the district R+11 (due in part to partisan gerrymandering that the state Supreme Court recently ruled unconstitutional).

But now, it’s looking like Democrat candidate Conor Lamb is in a dead heat with Republican Rick Saccone. Last week, the Cook Political Report declared the race a toss-up, moving it away from its previous “lean Republican” rating.

The momentum is continuing for Lamb; the latest poll from Monmouth University has the Democrat leading Saccone, using three different turnout models. For instance, if there’s a Democratic surge like there has been in recent special elections, Monmouth put Lamb with a 51 percent to 45 percent lead over Saccone. Using a model with lower turnout, Lamb still had a slight edge over Saccone, leading him 49 percent to 47 percent.

When Monmouth polled Pennsylvania voters last month, Saccone was the one in the lead.

This is a big deal for a seat that used to be so solidly Republican, Democrats didn’t compete in it. The newly open seat was held by former Rep. Tim Murphy (R-PA) since 2003, who was so secure in his seat that he often failed to attract a Democratic challenger. Murphy suddenly resigned in October amid revelations that he had pressured a woman with whom he was having an extramarital affair to have an abortion. But even after he stepped down, national Democrats didn’t think they could compete in the special election, a Democratic Congressional Campaign Committee operative told Vox.

That was, until Conor Lamb came along.

Lamb is a 33-year-old Marine and former assistant US attorney who prosecuted drug dealers in the midst of Pennsylvania’s deadly opioid crisis. New to politics, he has struck a decidedly independent tone, making headlines when he said he would not support House Minority Leader Nancy Pelosi as the Democratic leader if a blue wave sweeps the House in 2018.

“He’s got local ties; he’s a local guy,” said Tim Waters, political director for the United Steelworkers Political Action Committee. “He’s a young guy with a lot of energy ... right down the line on issues that affect workers in this district.”

Focused almost exclusively on local issues, Lamb has nevertheless stumbled into a long-running debate about how the Democratic Party can claw its way back to the majority after 2016.

Trying to recapture blue-collar workers, Lamb’s campaign represents one school of thought — going back to labor-liberal economic values and working with unions to retake territory in Midwest and Rust Belt states that voted for Donald Trump in 2016. Others say the party must look to its future: voters of color and young people who represent its energized base, like it did to pull out a win for Doug Jones in Alabama’s December special election for US Senate.

Still others, including former Vice President Joe Biden, say Democrats can do both. At a recent speech in front of House Democrats, Biden said the notion that Democrats have to choose between blue-collar workers and their progressive base was a “false debate.”

“It’s a false debate we’re having among ourselves, in my opinion,” he said. “Let’s not rip ourselves apart in a debate that is irrelevant.”

Democrats are in a good position going into the 2018 midterms, especially given the current backlash against Trump and the Republican-controlled Congress. This is in part due to fundamentals that favor the party out of power in midterm elections, but President Trump’s unpopularity has also given Democrats across the country something to rally around. And special elections have been very good for Democrats so far; they have swept a number of state races in red districts in Virginia, Wisconsin, and Kentucky, plus the Senate race in Alabama.

Lamb rarely mentions Trump in his campaign speeches. But his candidacy is an important post-2016 test of whether the party can successfully run moderate candidates in deeply red Rust Belt districts that swung for the president two years ago.

Even if Lamb loses in March, he’ll have another opportunity to compete again in the fall in an 18th District that looks different (and more favorable to Democrats), given the new congressional map drawn up by Pennsylvania’s Supreme Court. But if he wins, it will be another sign that Democratic momentum is strong and barreling toward November.

Who’s on the ballot on March 13

Lamb’s opponent is Pennsylvania state Rep. Rick Saccone, a Republican who has described himself as “Trump before Trump was Trump.” Trump is certainly popular in the district, which he won by 20 points in 2016 (Mitt Romney won it by 16 points in 2012). Saccone is a decidedly conservative Republican who is pro-life, pro-gun, anti-government spending, and — perhaps most importantly in this heavily unionized district — vehemently anti-union.

“Saccone is a movement conservative,” said Mike DeVanney, a longtime Republican political operative in Pennsylvania who worked on past Murphy campaigns. “His base is much more to the right than Murphy’s was.”

DeVanney described the likelihood of a Democrat winning the 18th as a “herculean task,” especially considering Republican-allied groups were outspending Democrats 17 to 1 for much of the race (although Lamb’s latest fundraising numbers show he’s making a dent in that).

Republican and Democratic operatives in Pennsylvania agree on two things: Lamb is still very much the underdog in this race, but by getting support from unions that used to back Murphy and capitalizing on national Democratic enthusiasm, he has a fighting chance. (Lamb’s campaign did not make him available for an interview despite repeated requests from Vox. Saccone’s campaign also did not return an interview request.)

This is reflected in recent poll numbers showing Saccone’s former double-digit lead has diminished significantly. A recent Monmouth poll shows the Republican with a slight lead, hovering around 49 percent to 46 percent (models with lower turnout give Saccone a slightly larger lead). Given the steep odds, these numbers are extremely good for Lamb.

“It’s enthusiasm I haven’t seen for a Democratic candidate for a long time,” said veteran Pennsylvania Democratic political consultant Mike Mikus, who lives in the 18th Congressional District. “I don’t think the national Republicans would be spending all this money if they thought it was a slam-dunk.”

What kind of Democrat can win PA-18?

If Lamb is going to win on March 13, political experts say he needs to straddle a moderate political line, which he’s so far been able to do.

There are technically 70,000 more registered Democrats in the 18th Congressional District than Republicans, but many of those voters have been casting ballots for GOP candidates for years. Mikus, who has worked on Democratic campaigns in the state for years, says Lamb needs to prove himself as an independent if he’s going to win over these voters.

“It’s not so much a conservative district as it is an economic populist district,” he said. “You don’t have to support the NRA down the line, but respect the right of people to own firearms ... and [be] someone that’s willing to stand up to the national party when they feel it’s in the interest of the district or the region.”

Though Lamb is from a well-known Pittsburgh Democratic family (his grandfather served as the Pennsylvania state Senate Democratic majority leader), it’s his first time running for office. He is keeping a careful distance from the national political party, drawing notice for his comments on Pelosi and not accepting Super PAC money.

His platform hits a lot of Pennsylvania’s biggest issues: jobs, protecting entitlements like Social Security and Medicare, organized labor, and helping end the heroin crisis currently ravaging the state. And he’s not trying to model himself as a progressive darling; a practicing Catholic, he says that while he personally opposes abortion, he supports Roe v. Wade as the law of the land. As a veteran, he is also pro-Second Amendment.

“Conor, I think so far, has done a fairly good job as portraying himself as someone that’s going to fight for the region,” Mikus said. “He’s obviously getting outspent, but I think he’s saying the right things on TV and on the stump.”

Saccone and the Republicans have an obvious advantage when it comes to money; the national Republican Party and conservative groups are dumping cash into the race and bringing out the big players to stump for Saccone: President Trump, Vice President Mike Pence, and Ivanka Trump have made all made public appearances with the candidate.

Saccone is also benefiting from a deluge of outside spending. As of early Feburary, the Washington Post’s Dave Weigel and Michael Scherer estimated Republican-allied groups had spent about $4.7 million in television and radio ads compared to the approximately $300,000 Democratic groups have raised for Lamb.

But when it comes to the campaigns themselves, Lamb is outraising Saccone 2 to 1, and his fundraising pace has picked up noticeably in the past few weeks. Federal Election Commission records show Lamb raised $3.2 million in the first seven weeks of 2018. Compared to that, Lamb finished 2017 having raised about $557,551. Lamb has also been able to blanket the television and airwaves with his own ads, counterbalancing the Republican attack ads against him.

Meanwhile, Saccone raised a total of $214,675 (he hasn’t yet released an updated campaign filing). A chunk of that was not fundraised — Saccone loaned himself $11,000, and his campaign transferred another $41,899 over from a previous committee financing a Senate bid of Saccone’s that never got off the ground.

Political operatives say it’s another indication of the enthusiasm behind the Democrat. And in a race that’s sure to be spun as a referendum on Trump’s presidency no matter who wins, many say it’s much more about the two candidates and the local issues in the 18th.

“This is hopefully going to be about these two candidates,” Waters said. “If it is, Conor Lamb is a rising star.”

The Democrats’ best hope might be aligning with unions

Even though PA-18 is a deeply red district, it’s also strong union territory. It contains more than 87,000 union members and their family members, everyone from building trades to energy workers to teachers.

Steelworkers are active, and although the district’s coal mines have been closing down, tens of thousands of retired union coal workers and their spouses remain in the area. Mikus estimated they could make up 20 to 25 percent of the electorate, while a DCCC operative estimates it’s closer to 30 percent.

Labor union members were also a huge demographic for Trump in 2016; after the presidential race, national exit polls showed Democrat Hillary Clinton had captured 51 percent of union households, 7 points less than President Obama in 2012. Meanwhile, Trump captured 42 percent of union households, a slight bump from Mitt Romney in 2012.

Former Rep. Tim Murphy, the onetime chair of the Congressional Steel Caucus, courted building trades unions for years and won the support of many. Saccone is doing the exact opposite, currying favor from right-to-work groups via his reputation for authoring state bills trying to end paid union leave for teachers who were working for their unions outside of the classroom, and voting for other bills targeting unionized workers.

“Unlike Tim Murphy, who really made his career as a Republican reaching out to labor ... Rick Saccone is the exact opposite,” Mikus said.

Waters, the political director for the United Steelworkers PAC, put it another way.

“Tim Murphy was more of candidate that would say what he thought people wanted to hear,” Waters said. “Rick Saccone is a zealot. Murphy was more like, ‘Test the water.’ This guy just jumps in with a belly flop.”

That’s having an impact among union leaders, even ones who spent years supporting Murphy. Nearly all the major unions have thrown their support behind Lamb and are helping him mount an organized door-knocking campaign throughout the district.

“I think most of the building trades who had supported Murphy and helped give him large margins are going to the Democrat,” said DeVanney, the Republican strategist.

What’s yet to be seen is whether union leaders can successfully convince their rank and file to go to the ballot box and cast their votes for Lamb in March. But they are certainly trying; Waters said political and union organizers have already knocked on tens of thousands of doors and will hit more in the coming weeks. He compares the enthusiasm to Alabama’s special election that helped propel the state’s first Democratic candidate in 25 years to the US Senate.

“We’re the biggest union in this congressional district,” Waters said. “We’re going to work until the last minute on Election Day. We’re going to make sure we talk to every single union voter,” as well as retirees and their families.

Lamb’s performance in the special election is a test case for what could happen in November

Even if Lamb loses, he’ll have a completely different district to compete in during future races (should he decide to do so).

In 2010, Pennsylvania’s Republican-controlled state legislature drafted congressional maps that made it near impossible for a Democrat like Lamb to win in the 18th District.

As Vox’s Andrew Prokop wrote:

Ugly-looking districts don’t always point to gerrymandering, but in this case, they do — Republicans tried to pack Democratic-leaning areas together into very few districts while surrounding the state’s big cities with districts Republicans would win comfortably. To get a sense of how powerful Pennsylvania’s gerrymander was, consider that in 2012, Democratic candidates won slightly more votes in US House elections and Barack Obama won the state. But the state’s 18 House seats didn’t split 9-9 between the parties — instead, Republicans won 13 seats there, and Democrats just won five. No seats changed partisan hands in the 2014 or 2016 elections, either.

But given a recent Pennsylvania Supreme Court ruling that resulted in the state redrawing its congressional districts, the updated 18th District will include parts of liberal Pittsburgh, which should make it much friendlier to Democrats. It’s far from the only district that’s changing; the new map reflects population changes more accurately, splits fewer counties, and will likely lead to many more competitive elections between Democrats and Republicans.

These changes won’t kick in by March 13, so Lamb and Pennsylvania Democrats have extra incentive to see if they can pull off a long-shot campaign in a district where the odds are still stacked against them. They feel confident, and cautiously optimistic.

“I like the choice in this thing,” Waters said. “I like our chances.”