Democrat Conor Lamb has a four-point lead over Republican Rick Saccone in a new poll released Friday, days before a special election for the House seat in Pennsylvania.

Lamb, a former federal prosecutor and Marine veteran, leads the GOP state legislator by 48 percent to 44 percent in the new RABA Research poll. It was first published by Talking Points Memo.

If Lamb wins, it would be an upset given the fact that the Pittsburgh-area district was taken by President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE in the 2016 election by nearly 20 points.

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Recent polls have shown Lamb with a consistent lead, however, and the RABA poll gives him his biggest lead yet.

Other polls have shown his support growing in recent weeks despite the millions of GOP dollars being poured into his opponent's campaign.

The two are campaigning for former Rep. Tim Murphy Tim MurphyBiden receives endorsements from three swing-district Democrats A federal abortion law might be needed Female Dems see double standard in Klobuchar accusations MORE's (R-Pa.) seat. Murphy resigned in October.

The moderate Democrat's campaign has bested Saccone's in fundraising, and Lamb outspent Saccone on radio and television ads. Saccone has taken heat from the House GOP's campaign wing for his tepid fundraising efforts in a district that party leaders thought they had in the bag.

The poll surveyed 707 likely voters in the district from March 6-8. Forty-one percent of those polled identified as Democrats, while 40 percent identified as Republican. The poll has a margin of error of plus or minus 3.7 percentage points.