Retired astronaut Mark Kelly’s campaign has raised more than $1 million in individual contributions since he announced he on Tuesday he's seeking the Democratic nomination to challenge Sen. Martha McSally, R-Ariz., in 2020.

"A huge thank you to everyone who saw our launch and joined our team yesterday," Kelly tweeted Wednesday morning. "I'm new to this, but I'm told we did well. In the first 24 hours we raised $604K from more than 9,700 contributions. We're #FullSpeedAhead without a DIME of corporate PAC money."

Kelly’s campaign spokesman, Rodd McLeod, shared later on Wednesday that the campaign had raked in $1.1 million, according to the Arizona Republic.

Kelly, 54, is married to former Arizona Rep. Gabby Giffords, and previously was a NASA astronaut. He also served in the Navy as a pilot and engineer, and flew 39 combat missions during the 1991 Gulf War before he retired as a captain.

Kelly and Giffords founded Americans for Responsible Solutions, a nonprofit organization that supports gun control, after Giffords was shot in the head during a meet-and-greet.

“I always knew that I was going to serve this country in some way,” Kelly said in his campaign announcement. “What I learned from my wife is how you use policy to improve people’s lives.”

[Also read: Arizona Sens. Kyrsten Sinema and Martha McSally have one thing they agree on: They hate each other]

McSally, a former Air Force colonel, who was appointed to fill the seat by Arizona Gov. Doug Ducey last year to replace former Republican Sen. Jon Kyl. Previously, a member of Congress for 26 years, Kyl was tapped after Sen. John McCain, R-Ariz., died in August, but he stepped down in December to return to his lobbying firm Covington & Burling.

The special election in 2020 will determine who will serve until 2022, the final two years of McCain’s term. Another election for the seat will be held in 2022.