(CNN) Nearly one month after his upset victory in Pennsylvania's 18th District special election, Democrat Conor Lamb was sworn into the House of Representatives on Thursday evening by outgoing Speaker Paul Ryan.

Lamb will serve out the remaining eight months of former Republican Rep. Tim Murphy's term

Lamb was the first, and so far only, Democrat to flip a House seat out of the seven special elections held during Donald Trump's presidency. There are two more special elections scheduled between now and November.

"We are all in this together, we need solidarity with each other," Lamb said during his first remarks on the House floor, in a call for more bipartisanship.

Lamb's March 13 victory helped boost Democratic enthusiasm and optimism heading into the stretch through November. Democrats now need a net gain of 23 seats in the fall midterms to take back the House.

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