Democrats must defend 23 seats, compared to just 11 for Republicans and nearly all competitive seats are currently held by Democrats, putting them on the defensive as they try to maintain their slim majority.
The haul comes after Wilson announced a record-breaking sum of $2.2 million last quarter, which is the most money raised by a GOP Senate candidate or potential candidate in their first three months.
Roosevelt Mayor Rod Bird Jr. announced his Senate campaign on Monday afternoon, making him the fourth candidate to officially launch his bid after Romney confirmed last week he would be retiring once his term expires in 2024.
Sen. Mitt Romney (R-UT) publicly questioned why Senate Minority Leader Mitch McConnell (R-KY) polls so poorly during a press conference after announcing his retirement from the Senate on Wednesday.