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

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.

President Trump visited the district just last week but the White House insisted the trip was solely to tout the economy and recently-passed tax reform bill.

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.

A nonprofit group called Ending Spending -- founded by Chicago Cubs co-owner Joe Ricketts - kicked off the flow of Republican money into the race earlier this month, rolling out ads costing $513,386 to support Saccone and attack Lamb.

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

And a pro-Trump nonprofit named 45Committee - also a 501(c)(4) - just last week spent $518,640 on an ad campaign to benefit Saccone. Founded by megadonors Sheldon Adelson and another Cubs co-owner, Todd Ricketts, 45Committee dropped a total of $21.3 million to support Trump during the presidential election.

A third group, Congressional Leadership Fund (CLF), a super PAC with ties to House Speaker Paul Ryan, R-Wis., reported spending $104,952 on ads backing Saccone earlier this month.

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.

With Election Day less than two months away, so far there's been no outside spending from the Democratic side reported to the FEC.

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.