The Democratic and Republican Senate campaign arms both raised $4 million in December, according to figures released Friday.
The month ended a strong fundraising year for the Democratic Senatorial Campaign Committee, which outraised its Republican counterpart by $16 million on the year.
The DSCC, which raised $52.6 million in 2013, paid down its debt to $3.75 million and ended the year with $12 million in cash on hand.
The National Republican Senatorial Committee, which got off to a slow start in 2013, raised $36.7 million last year and ended December with $8 million on hand and no debt.
Republicans must net six seats to win the majority in November.