After losing their majority in 2014, Senate Democrats are trying to make a comeback by out-fundraising their Republican counterparts for the fourth time in six months.

Last month, the Democratic Senatorial Campaign Committee raised $5.6 million, according to its latest fundraising report.

While the NRSC touted its $4.1 million haul as a new record for an off year, Senate Republicans still came up $1.5 million short of their Democratic rivals.

Between January-March 2015, Senate Democrats maintained a three-month lead in fundraising over the GOP, giving them a $3 million lead over the NRSC in the first half of 2015.

"Republicans and their special interest allies have already spent over $3 million to attack our candidates and prop up their increasingly vulnerable incumbents," DSCC executive director Tom Lopach said in a statement. "The resources we have raised will allow us to expose the anti-middle class agenda of the Republican Senate and the contrast they have with our outstanding crop of candidates."

The Democrats lost the Senate in 2014, when the party had to defend vulnerable seats and there was a Republican wave. Now the shoe is on the other foot. In 2016, Democrats have only 10 seats to defend, and Republicans have 24 — including seven in states that President Barack Obama won twice.

In order to win back the majority, Democrats would need to win at least four seats in the 2016 election. That number grows to five if a Republican wins the White House because the vice president votes in the case of ties.

Sen. Michael Bennet, D-Colo., is considered vulnerable and Democrats will have to defend Senate Minority Leader Harry Reid's seat in Nevada. Reid, who was likely to face a tough re-election, has announced his retirement.

But Democrats are hopeful that the number of races in expected presidential battleground states will lead to increased voter turnout, particularly among women and minorities.

"Presidential campaign cycles bring with it the potential for a tremendous amount of voter enthusiasm, and when you look at the 2016 map and the numerous vulnerable Republican senators who are on it, that can only help Democrats," Justin Barasky, a DSCC spokesperson told the Wall Street Journal.

As previously reported by the Washington Examiner, Senate Democrats are expected to recruit strong candidates to challenge vulnerable Republican Sens. Mark Kirk, R-Ill.; Ron Johnson, R-Wis.; Pat Toomey, R-Penn.; Kelly Ayotte, R-N.H.; Rob Portman, R-Ohio; and Marco Rubio, who has retired in order to run for president.