A Democratic candidate has outraised Texas Sen. Ted Cruz Rafael (Ted) Edward CruzVideo of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Democrat on Graham video urging people to 'use my words against me': 'Done' MORE (R) so far in 2018, posing a possible challenge for the well-known Republican firebrand in the upcoming midterm elections.

El Paso Rep. Beto O'Rourke’s campaign raised $2.3 million in the first six weeks of the year, federal filings show, topping Cruz's $800,000 over the same period.

"This is serious," the Cruz campaign told its donors in a message after the O'Rourke campaign reached the $2 million mark after just 45 days of fundraising in 2018, according to The Dallas Morning News.

ADVERTISEMENT

Cruz, a former 2016 GOP presidential contender, remains on top in cash on hand, with $6 million compared to O'Rourke's $4.9 million total.

Cruz has also outspent the Democrat in the opening volley before the March 6 primaries.

O'Rourke is gaining momentum in the race, and has surpassed Cruz in fundraising for the last three of four reporting periods for campaign finances, the outlet reported.

Republicans hold only a narrow majority in the Senate, with Democrats gunning to take back the House in 2018.