Louisiana's Foster Campbell is running for the Senate as a "conservative" Democrat, but his largest contribution in the past month came from the Senate's most liberal member, Sen. Elizabeth Warren (D., Mass.).

Campbell's bid to win this weekend's runoff election in a state where Donald Trump won by 20 points hinges on his ability to win Republican-leaning voters. He has stated he is "pro-Second Amendment and pro-life," putting him at odds with most of his party, but his status as the Democrats' last hope to make gains this election has made him a darling of left-wing activists since Election Day.

One of those activists is Warren, who contributed $5,000 to Campbell through her PAC for a Level Playing Field on Nov. 18, according to his campaign's most recent campaign filing.

Campbell is not the usual candidate Warren's PAC supports—every other Senate candidate it gave money to this cycle aligns closely with Warren on abortion and gun rights. Warren's PAC did not contribute to Campbell during the general election, but decided to support him now that he is the only Democrat left.

The support from Warren, who has been graded as the Senate's most liberal member, hasn't changed the way Campbell is running in Louisiana.

Just a week after the contribution, Campbell's allies began an ad campaign attacking his Republican opponent for having ties to Planned Parenthood, a group that gives Warren a perfect 100 percent rating.

Many of Campbell's campaign ads end with him shooting one of his shotguns (Campbell says he owns 37 of them). Warren has vowed that the National Rifle Association "will be defeated."

Campbell acknowledged his differences with Warren but said they "share a passion for making government work for our people."

"Senator Warren knows we don't have to agree on everything as long as we agree that Congress should serve our people, not special interests," Campbell told the Washington Free Beacon. "Although she and I do not see eye to eye on some issues—for instance I’m pro-life and pro-Second Amendment—we share a passion for making government work for our people."

Warren's support of Campbell indicates that she thinks he would be an ally in the Senate despite their differences.

Like Warren, Campbell opposes Trump's proposed border wall and is against repealing Obamacare. Campbell is also a self-described populist with a "fondness" for bashing the oil industry and other large corporations.

However, Campbell has said that he will "work with" Trump "when he's right." He refused to support Democrat Hillary Clinton in the presidential election.

A political expert in Louisiana told the New York Times that there is not "a smidgen of difference" between Campbell and his opponent, unless Campbell is given "a chance to attack oil and gas."

Campbell's campaign did not respond to questions on whether he has been in communication with Warren.

UPDATE, Thursday 12:50 P.M: This post has been updated to include comment from Campbell.