Editor's note: This story has been updated to reflect U.S. Sen. Ted Cruz's fundraising numbers.
O'Rourke raised $2.1 million in his first quarter as a U.S. Senate candidate, according to a statement he released on Thursday morning. The Cruz camp followed up later in the day stating the incumbent raised $1.6 million.
Cruz still has a significant cash-on-hand advantage with $5.7 million, while O'Rourke is expected to report just shy of $1.9 million in cash on hand.
O'Rourke's haul – the first fundraising quarter of his Senate bid – also surpassed the fundraising of some U.S. Senate Democratic incumbents in other states who are the subject of major party pushes to hold their seats in 2018.
Texas, in comparison, is far less of a priority for the national party because of its size, conservative makeup and the high cost of advertising in the state.
"We raised more than $2 million over the last three months, from more than 45,000 unique donations, most of them from Texas, every one of them that wanted to take back our state, take back the senate and take back this country," O'Rourke said.
He added that none of that money came from "PACs or special interests or corporate donors."
The junior senator from Texas had a fierce fundraising machine during his unsuccessful bid for the Republican presidential nomination in 2016, and acquired a massive conservative following. At the same time, O'Rourke has deftly built an online following in recent months and standing-room only crowds have shown up at his events across the state. But he is still mostly unknown and on his own in this race.
The challenger will need every dime he can raise to build up his name identification. And for now, it is unlikely the national party will help him in this effort as they focus resources on other states.
National Democrats say they will prioritize supporting the ten Senate incumbents who represent states President Donald Trump carried in 2018.
Patrick Svitek contributed to this report.