Pence to campaign for Republican in Pa. special election as outside money floods in

The special election in Pennsylvania's 18th district will take place March 13.

— -- Vice President Mike Pence will head to Pennsylvania’s 18th district next month to campaign for Republican candidate Rick Saccone in a special election that's ignited new GOP anxieties that it might lose another race ahead of the 2018 midterms.

Pence’s visit on Feb. 2, confirmed by Saccone’s campaign to ABC News, will be the first official White House involvement in the race.

During his visit Trump praised Saccone as a “great guy” and promised to return to the district before the March 13 special election between Saccone, a state senator and former military intelligence officer, and Democrat Conor Lamb, a Marine Corps veteran and former federal prosecutor.

As the race continues to cause greater GOP concern, elites and mega-donors in the national party have started ramping up outside spending in the race.

Established as a 501(c)(4) organization, Ending Spending is not required to disclose its donors.

CLF also announced earlier this month that it is opening two field offices in the district and employing 50 full-time door knockers with a goal of reaching 250,000 voters before March 13.

Lamb faces an uphill battle in Pennsylvania’s 18th district, which is tucked in the state’s southwestern corner. The district voted for President Trump by nearly 20 points in the 2016 presidential election, and had been represented by Rep. Tim Murphy, R-Pa. since 2003.

Murphy resigned after it surfaced that he not only had an extra-marital affair, but that he urged his mistress to get an abortion after she discovered she was pregnant. Murphy was an ardent anti-abortion voice in Congress.

ABC News' Adam Kelsey contributed to this report.