Democratic candidate Conor Lamb won a narrow victory over Republican Rick Saccone in Tuesday’s special House election in the 18th congressional district of Pennsylvania. The district occupies the southwest corner of the state, a former steel and coal-producing region that includes the southern suburbs of Pittsburgh. It backed Trump over Democrat Hillary Clinton by a 20-point margin in 2016.

With all precincts and absentee ballots counted in the four counties that make up the district, Lamb had a lead of 627 votes, 113,813 to 113,186. Lamb claimed victory, and both the television networks and local newspapers called the result in his favor. However, Saccone and the Republican Party have not yet conceded, discussing their options for a recount or challenge to the result.

Assuming the result stands, the special election would be the first in which a House seat changed parties since Trump took office. In the four special elections in 2017 caused by Trump’s appointment of Republican congressmen to cabinet posts, there were major swings to the Democratic Party, but Republicans still held the seats, albeit by diminished margins.

The vacancy in the 18th congressional district was caused by the resignation of longtime Representative Tim Murphy, a Republican who did not even face a Democratic challenger in 2014 or 2016. Murphy, a right-wing opponent of abortion rights, resigned after it was revealed that, in the course of an extramarital affair, he had pressured his mistress to get an abortion.

Tuesday’s vote has national implications, since there are 114 congressional districts held by Republicans that voted for Trump in 2016 by a smaller margin than the southwest Pennsylvania district. All of those districts are thus potential targets for Democratic takeover, under conditions in which the Republican majority in Congress—after the Pennsylvania defeat—is down to 23 seats.

The Democratic leadership in Washington fears more than anything else a sharp swing to the left in popular sentiment in reaction to the attacks on democratic rights and social programs being carried out by the Trump administration and the Republican Congress, as well as its huge tax cuts for corporations and the wealthy.

The Democratic Congressional Campaign Committee has set up a firewall against such a development by promoting more right-wing candidates in party primaries, particularly those with a military-intelligence background, as well as policemen and prosecutors. Lamb, age 33, a recent Marine veteran and current federal prosecutor, checked both boxes.

In the event of a sweeping Democratic victory in November, there will be an influx of new members who come to Congress for previous service in the CIA, the military, the State Department or the National Security Council.

A WSWS analysis published last week identified 57 candidates with a military-intelligence background seeking Democratic congressional nominations in districts identified by the DCCC as competitive. This compares to only 19 military veterans in the current Democratic caucus in the House, out of 193 members.

Lamb is the first of the 57 military-intelligence Democrats to be elected to Congress. His opponent, Rick Saccone, had a similar background, with a much longer career in Air Force intelligence, including multiple deployments to South Korea, before he retired and went into local politics, winning four terms in the Pennsylvania state legislature.

Saccone campaigned on a typical Republican ultra-right program, combining appeals to right-wing religious groups on abortion and gay rights with overt hostility to unions—in a district with at least 80,000 union households, including 20,000 current and retired steelworkers and nearly that many coal miners, most of them retired or unemployed.

It was Saccone and the Republicans who chose to make the contest a referendum on Trump, evidently assuming that this strategy would be successful in a district Trump carried so easily in November 2016. While Lamb raised $3.9 million for the race, itself a huge sum for a brief congressional campaign, Republican Party organizations poured in more than $10 million. Trump visited the district twice for campaign rallies, while family members and other Trump surrogates were campaigning with Saccone continually.

The Democratic candidate offered a series of olive branches to the right, declaring his “personal” opposition to abortion, although he said it should still be legal, affirming his opposition to any form of gun control, including limits on the possession of assault rifles, and opposing a proposed increase in the statewide minimum wage to $15 an hour.

When he faced Republican attack ads saying that he would represent another vote in Congress to make Nancy Pelosi the Speaker of the House again, Lamb responded that he would not vote for Pelosi as the Democratic leader.

Despite that disavowal, Lamb is a scion of the Democratic Party establishment: his grandfather was Democratic leader in the state senate, and his uncle is the current city controller in Pittsburgh. He did not win the Democratic nomination in a primary, but was selected over six rivals by a party committee after the incumbent unexpectedly resigned.

While benefiting from popular anger against Trump, Lamb himself said virtually nothing critical of the president, going so far as to declare that Trump was not even an issue in the election campaign, which revolved around purely local concerns.

Perhaps the most important factor in Lamb’s campaign was the full backing of the unions, particularly the steelworkers and coal miners, whose retirees make up a huge percentage of the 18th district’s population. Saccone campaigned as a supporter of a state right-to-work law, which would threaten the dues income that finances the lavish perks and salaries of the union officials. Lamb opposed such a law. Both candidates endorsed Trump’s imposition of tariffs on imported steel and aluminum, which the unions enthusiastically supported.

The United Mine Workers union, which did not support Hillary Clinton against Trump, campaigned heavily for Lamb, and even tried to associate the Lamb campaign with the struggle by teachers taking place only a few miles away, across the state line in West Virginia.

At a rally for Lamb in a former mining town, Waynesburg, the candidate said only a few words, the usual mush, while UMWA President Cecil Roberts hailed him as a “a God-fearing, union-supporting, gun-owning, job-protecting, pension-defending, Social Security-believing, sending-drug-dealers-to-jail Democrat.”

Such language only testifies to the entirely right-wing political orientation of both the unions and the Democratic Party, which are the principal obstacles to the development of an independent political movement of the working class against the Trump administration, the corporate-controlled two-party structure, and the capitalist system as a whole.