Retired astronaut Mark Kelly’s Arizona Senate campaign announced Wednesday that it has raised an eye-popping $4 million in the first quarter of 2019.

The campaign said its haul was driven by more than 58,000 contributions, 96 percent of which were $100 or less. The average online contribution was $25, Kelly's campaign said.

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“Our campaign is fueled by supporters from all walks of life chipping in what they can because they want a voice in their democracy and they know Mark will be an independent leader for Arizona,” campaign manager Jen Cox said in a press release. “We’re proud of the cactus roots campaign we are building with contributions from each of the fifteen counties in Arizona and without a dime from corporate PACs.”

Kelly has high name recognition as a former astronaut and as husband to former Rep. Gabrielle Giffords (D-Ariz.), who narrowly survived a shooting in 2011. The couple has since been a high-profile duo advocating for gun law reform.

Kelly is running to face off against Sen. Martha McSally Martha Elizabeth McSallyTumultuous court battle upends fight for Senate Grassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee The Hill's Campaign Report: Biden goes on offense MORE (R) to serve the remaining two years of the late Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE’s (R) seat. McSally was appointed to the Senate in December after McCain’s death in August, with former Sen. Jon Kyl (R) serving in the interim months.

McSally’s campaign has yet to release its first quarter fundraising haul.

It appears unlikely that the former astronaut will face a serious primary challenge after Rep. Ruben Gallego Ruben GallegoHispanic caucus report takes stock of accomplishments with eye toward 2021 Senators call on Pentagon to reinstate funding for Stars and Stripes newspaper Hispanic Caucus campaign chief to mount leadership bid MORE announced last month he would sit out a Senate bid.

Democrats see the Arizona Senate race as one of their top pickup opportunities after Kyrsten Sinema (D) defeated McSally last year in the race to replace the retiring Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (R).