Vulnerable incumbent Senate Democrats raked in massive fundraising hauls in the last quarter of 2021 as they work for a financial advantage going into what are expected to be tough midterm elections. 

In Arizona, incumbent Sen. Mark Kelly (D) brought in a whopping $9 million during the fourth quarter, leaving him with $18.5 million in the bank. 

The haul puts Kelly far ahead of his Republican challengers. Venture capitalist Blake Masters raised $1.38 million during the same period, while Arizona Attorney General Mark Brnovich (R) took in $800,000 during the fourth quarter. Army veteran Jim Lamon is mainly self-funding his Senate bid in the state. 

Meanwhile, in New Hampshire, Sen. Maggie Hassan's (D) reelection campaign shored up $3.1 million in the final quarter of the year. Hassan's latest haul brings her campaign's cash-on-hand total to $5.3 million.

The Granite State's GOP Senate primary field is still coming together after national Republicans failed to recruit Gov. Chris Sununu to run for the seat last year. Retired Army Gen. Don Bolduc was the first Republican to declare last year, while state Senate President Chuck Morse (R) announced on Monday he will challenge Hassan, and Londonderry, N.H., town manager Kevin Smith is expected to jump into the intraparty contest imminently. Morse is known for being a strong fundraiser in New Hampshire. 

And in Nevada, Sen. Catherine Cortez-Masto (D) brought in more than $3.3 million at the end of the year, bringing her cash-on-hand total to $10.4 million. Cortez-Masto's Republican challengers, former Nevada Attorney General Adam Laxalt and Sam Brown, have not yet released their fourth-quarter fundraising numbers. 

Kelly, Hassan and Cortez-Masto are seen as some of the more vulnerable Democrats in the Senate facing reelection this cycle. The nonpartisan Cook Political Report rated Kelly's and Cortez-Masto's race as "toss-ups," while Hassan's race is "lean Democratic." 

The Democratic Senatorial Campaign Committee (DSCC) touted the latest fundraising hauls in a statement to The Hill. 

“Another record-breaking fundraising quarter for our Democratic Senators shows the power of their grassroots support, and momentum for Democrats’ work in the Senate to lower costs, grow millions of good-paying American jobs, and cut taxes for families," said DSCC spokesperson Jazmin Vargas. 

Of course, the fundraising has the potential to narrow once the races head into the general election. National Senate Republicans are also bringing in large sums of cash ahead of the midterms.

The National Republican Senatorial Committee said this week it brought in $28.6 million in the final quarter of 2021, bringing its total for 2021 to $104.8 million. The GOP committee currently has $32.7 million in the bank.

The DSCC has not yet released its fourth-quarter fundraising totals.