Democrat Conor Lamb, a former U.S. attorney and Marine Corps veteran running to represent Pennsylvania’s 18th Congressional District, leaves an American Legion post after a rally Jan. 13 in Houston, Pa. (Jeff Swensen/Getty Images)

Democrats are firing up the attack machine in the race for Pennsylvania’s 18th Congressional District, with Democratic nominee Conor Lamb responding to a barrage of super PAC ads with his first negative spots — and a growing theme that the Republican nominee puts government up for sale.

In the first new spot, Lamb attacks state Rep. Rick Saccone over a story, published first in the Intercept, about how Saccone paid for “meals, per diems, and lease payments to a political donor, all from an expense account paid for by the taxpayers.”

In the other — a response to a cavalcade of ads from the Congressional Leadership Fund, a super PAC aligned with House Speaker Paul D. Ryan (R-Wis.) — the Lamb campaign clarifies the Democrat’s opposition to the Tax Cuts and Jobs Act. “Many Pennsylvanians will have their tax cuts wiped out by higher health-care premiums,” it says, noting that Lamb would have backed “middle-class tax cuts” that did not explode the deficit.

The new spots, part of an estimated $400,000 ad buy, are designed to counter more than $4 million of mostly negative ads from national groups — the CLF, the National Republican Congressional Committee and Ending Spending. They come after the Lamb campaign grew frustrated with the lack of air cover from Democrats, whose investments in the race have been limited to a six-figure buy from the Democratic Congressional Campaign Committee. They’re the first negative spots Lamb has run, coming after bio spots introducing him and highlighting his military service. (A new CLF ad ties Lamb to the Iran nuclear deal because he worked for “the Obama administration” in his capacity as an assistant U.S. attorney.)

Republicans concede that Lamb’s campaign has kept the March 13 election — in a district that gave Donald Trump more than 58 percent of the vote — uncomfortably close. This week, Saccone, who has been criticized for low fundraising, will sit for a roundtable with the Business Coalition for Fair Competition, a group that works to end “utilization of and reliance upon the private sector by government at all levels and that eliminates unfair government-sponsored competition with private, for profit enterprise, including small business.” (Saccone’s campaign did not respond to a question about the group’s mission.)

President Trump is expected to visit the district soon, in what would be his second stop there. The first, a rally ostensibly held to promote the tax cuts, was errantly described by the president as a campaign event.

Lamb’s campaign used that visit to attract online donors; it has had help since then by Democrats outside the state who want to direct their supporters to a tight race that would break the party’s streak of single-digit losses in special House races. The latest help came from Randy Bryce, the high-profile challenger to Ryan in his southeast Wisconsin district.

“We don’t need more politicians in Congress who do nothing but cut taxes for corporations and millionaires,” Bryce wrote in a weekend email to his donor list. “We need leaders, like Conor, who will stand up to Paul D. Ryan, who aren’t afraid to say the word ‘union’ and who will do everything they can to make sure working people have a voice.”

The Pennsylvania race is for the seat vacated by Rep. Tim Murphy (R), who in October resigned after a report alleged that he asked a woman with whom he had an affair to get an abortion.