Update: Dan Donovan won the primary Tuesday with 64 percent of the vote to Michael Grimm’s 36 percent.

Tuesday is primary day in New York, and several races–almost all Democratic–are worth watching closely. In races such as NY-19 (Hudson Valley, Catskills) and NY-21 (North Country), crowded fields of Democratic hopefuls are duking it out for the privilege of challenging vulnerable GOP incumbents. In NY-9 (Brooklyn), NY-12 (Upper East Side, Queens) and NY-14 (Bronx, Queens), progressive insurgents are challenging entrenched incumbents in races where the Democratic nomination is tantamount to election.

None of these districts feature similarly heated GOP primaries, nor do almost any of the congressional districts in New York. But one race, New York’s 11th district, which covers all of Staten Island and parts of southern Brooklyn, is bucking the trend of non-competitive or non-contested GOP nominations. This race is pitting an establishment incumbent, Rep. Dan Donovan, against a Trumpier conservative, former Rep. Michael Grimm. This race promises to be as much a fight for the soul of the Republican party as any of New York’s other contested primaries are for the Democratic party.

The first thing that anybody learning about Staten Island politics needs to understand is that, despite being a borough of New York City, it is very much the black sheep of the family. “Staten Island has always been a red enclave in New York City,” says Michael Abel, a NY11 voter and former intern for Grimm, but who now says he supports Donovan. Whereas the other four boroughs are solidly Democratic, voting for Hillary Clinton by between 88.5% (Bronx) and 75.4% (Queens), Staten Island is much, much more conservative.

In 2012, Staten Island voted for Barack Obama by a 0.8% margin, compared to 81.4% in neighboring Brooklyn. But in 2016 it swung considerably, voting for Trump by a resounding 14 point margin. All the while, it has consistently sent Republicans to Congress since 1980, with only one two year period interrupting otherwise consistent GOP domination. In 2010, Staten Island elected Michael Grimm, a “tough guy” former FBI agent and businessman who was seen as a rising star in the party. That is, until he was brought down by a storm of scandals ranging from tax evasion and perjury, accepting improper campaign gifts, and threatening to punch a reporter. He would plead guilty to felony tax fraud for which he was sentenced to eight months in prison. Grimm was replaced by Republican Dan Donovan in a 2015 special election. Now the two are battling for the seat.

One key factor in this race, as well as midterm races across the country, is Trump. As was the case in the Republican primaries for West Virginia’s Senate seat and South Carolina’s 1st Congressional District, commitment to Trumpism and Trump’s endorsement have played a roles in the NY-11 race. Donovan has one of the most moderate voting records of any Republican member of Congress, having voted against key Trump legislation including the tax bill and the American Health Care Act. Despite this, however, Donovan received an endorsement from Trump, who said of Donovan, “There is no one better to represent the people of N.Y. and Staten Island,” and claimed he is, “strong on Borders & Crime, loves our Military & our Vets, voted for Tax Cuts and is helping me to Make America Great Again.” This should serve as a great asset to Donovan in a district that voted for Trump by a 72% margin in the 2016 Republican primary. In theory, that is.

Many Staten Island residents probably see the endorsement for what it is, a concession by Trump to establishment Republicans who certainly view Grimm as a catastrophic general election candidate due to his felony conviction. This skepticism is reflected in Grimm’s 10 point lead in a poll conducted by the reputable Siena Research Institute earlier this month, shortly after Trump’s endorsement of Donovan. An internal poll from Donovan’s campaign shortly after that showed Donovan up 7 points. That casts his lead in that poll into serious doubt. That poll also showed Grimm leading among voters who align themselves with Trump and the Tea Party

On the surface, Grimm seems to have the enthusiasm. “You drive around Staten Island and all you see is Grimm lawn signs, at least 10:1 compared to Donovan,” notes Abel, who believes that many residents still retain loyalty for Grimm after he shepherded and fought fiercely for Hurricane Sandy relief legislation in Congress. Staten Island is among the communities that were hit hardest by Sandy. Grimm has also staked out a firm position to the Trumpian-right of Donovan’s traditional conservatism. “He votes with the President on most bills,” notes Michael Flanagan, a professor of political science at CUNY Staten Island. But that hasn’t stopped Grimm from putting out ads painting Donovan as something of a never-Trumper. Flanagan adds that Donovan is vulnerable to these ads in part because he “hasn’t been able to articulate that [he’s a Trump loyalist] very well.” He also points out that in terms of persona, Grimm is much Trumpier than Donovan. “Grimm’s personality more closely matches Trump, that’s the bad boy stuff and that’s what’s got everyone’s attention,” he says.

So why does Trumpism play so well in Staten Island? And moreover, why hasn’t Trump’s endorsement done more to boost Donovan? “There’s a contrariness to the place,” says Flanagan, who says that Staten Islanders like “flipping the bird to the rest of the city, which is sort of like the Trump story.” He explains that anti-Grimm editorials in mainstream media outlets actually “strengthen the intensity of his support.”

Unlike the Republicans, the Democrats have a slightly more orderly primary. Their preferred candidate Max Rose, a Jewish army veteran and non-profit worker, is the frontrunner. But Flanagan remains a little bearish on Rose’s lock on the primary: “Rose as the annointed candidate? I don’t know about that,” he says.

Rose, for his part, views the Republican contest as essentially moot. “Besides some time in prison, they’re two sides of the same coin,” he said of Donovan and Grimm, adding, “They had their chance to change Washington. They failed.” Rose says his strategy to win is “to take nothing for granted,” and “to work extra hard to not just get 50.1 percent but, win by such a large margin neither one of them seeks public office again.” Lofty goals in such a Trumpy district.

This primary will serve as not only  a proxy for national intraparty clashes, but as a litmus test for whether this may be a wave year for Democrats. This is the only district in New York, and one of the few in the country,  that features at least somewhat competitive primaries for both parties. Due to its relative swinginess–”Democrats actually have a slight registration advantage,” Flanagan points out–turnout and net voters in the primaries could shed a light on the true size and power of the blue wave. Will it be the political equivalent of Sandy, shaking Staten Island to its very core? Or will it resemble the waters of Raritan Bay gently splashing the southern coast at low tide? We’ll find out soon enough.