Just as the Democratic Party’s process to select a candidate to challenge President Trump next year intensifies, with 20 declared candidates so far and the first debate set for next month, Democratic and Republican officials are wasting no time in focusing on New York’s First Congressional District. The online political magazine CQ Roll Call reported last month that the National Republican Congressional Committee has named Representative Lee Zeldin to a list of eight incumbents expected to face tough re-election campaigns. Only one of those eight, however, was in a race that the website Inside Elections considered a toss-up, CQ Roll Call reported, the others “tilting, leaning, or likely to remain Republican.” Inside Elections has New York’s First District in its “likely Republican” column. Mr. Zeldin, who is pictured under the CQ (Congressional Quarterly) Roll Call headline “House Republicans Identify Vulnerable Members for 2020,” is now one of 10 incumbent Republicans in the N.R.C.C.’s Patriot Program, which, according to its website, “empowers members to build strong and winning campaigns through goals, benchmarks, and accountability.” The site includes links to donate directly to the candidates. Mr. Zeldin won a third term last November, defeating Perry Gershon, an East Hampton resident waging his first political campaign, by 4 percentage points. Two years earlier, he easily fended off a challenge by former Southampton Town Supervisor Anna Throne-Holst, winning by 16 percentage points.Though he lost in New York, his home state, in 2016, Mr. Trump won the First Congressional District by 12 points. He also plans to seek re-election next year. Mr. Gershon, who last month announced his intention to challenge Mr. Zeldin again, seized on the N.R.C.C.’s move. “Connect the dots: This month, I asked for a rematch with Lee Zeldin,” an April 25 email soliciting donations began. “Shortly thereafter? Panic from their team,” with a reference to the CQ Roll Call Article. “National Republicans and Lee Zeldin are feeling the ropes. Our grassroots movement came so close to winning in 2018. In 2020, let’s get over the finish line and send Zeldin packing.”In January, the Democratic Congressional Campaign Committee, the party’s campaign arm for the House of Representatives, identified 33 Republican-held seats to target in next year’s elections, Mr. Zeldin’s among them. The same month, it attacked 25 House Republicans, including Mr. Zeldin, with Facebook ads tying them to the government shutdown of December and January. Last year, the D.C.C.C. included Mr. Gershon on its Red to Blue list of top-tier candidates to which it provides funding and organizational support. “I know they’re very interested in this race,” he told The Star last month. “I’m talking to them very frequently, so I know we are one of the target races.”For its part, in February the N.R.C.C. named 55 House Democrats it has targeted for defeat next year, most of them elected in November, when Democrats gained 40 seats and recaptured a majority in the House of Representatives.