Conor Lamb, Democratic congressional candidate for Pennsylvania's 18th district, greets supporters at an election night rally March 14, 2018 in Canonsburg, Pennsylvania.

Democratic Rep. Conor Lamb will emerge victorious from a clash of two incumbents in Pennsylvania's 17th District, NBC News projects.

In his second House election this year, he will flip Republican Rep. Keith Rothfus' seat. Lamb, who won a special election in a deep red southwestern Pennsylvania district in March, subsequently faced Rothfus due to redistricting in the state.

Lamb, a Marine veteran, used a campaign strategy employed by Democrats trying to win red-leaning House seats across the country. He pledged to stop cuts to social safety net programs, keep but fix the Affordable Care Act and protect labor unions.

President Donald Trump endorsed Rothfus more than once.

Democrats need to gain a net 23 GOP-held seats to win control of the House. Boosted by a favorable environment and the revision of a GOP-drawn congressional map, they hope to pick up a handful of those seats in Pennsylvania alone.