Democratic candidates in competitive Senate races received another surge in donations over the last few months, with some breaking fund-raising records in their states and many entering the final weeks of the campaign with significant stores of cash, according to new quarterly filings with election authorities this week.
ActBlue, the central platform for donations to Democratic candidates and causes, announced that from July 1 to Sept. 30, it had processed $1.5 billion in contributions — an amount roughly equal to what the site raised during the entire 2018 election cycle, and one far exceeding the $623.5 million that the equivalent Republican platform, WinRed, took in during the quarter.
Mark Kelly, the Democratic Senate candidate in Arizona, was among those who reported raising another enormous sum. Mr. Kelly’s campaign took in more than $38.7 million in those three months, and polls in the state show him with a widening advantage over the Republican incumbent, Senator Martha McSally. His campaign indicated that it had entered October with $18.8 million in cash on hand.
Ms. McSally’s campaign reported raising $22.6 million in the period, with nearly $12.2 million in the bank.
In the Kentucky Senate race, the Democratic candidate, Amy McGrath, raised $36.9 million in the quarter. Her campaign, seeking to unseat Senator Mitch McConnell, the majority leader, reported having nearly $20 million in cash on hand. Mr. McConnell’s campaign raised less than half of that, $15.8 million, and reported $13.9 million in cash on hand.
In Maine, the Democratic challenger, Sara Gideon, took in $39.4 million in her effort to unseat Senator Susan Collins, the Republican incumbent, whose campaign raised $8.3 million. Ms. Gideon reported $22.7 million in cash on hand, compared with nearly $6.6 million for Ms. Collins, who received an endorsement from former President George W. Bush in August.
Jaime Harrison, the Democrat challenging Senator Lindsey Graham, Republican of South Carolina, shattered the record for Senate campaign fund-raising in a quarter, taking in more than $57 million in the period in question. Mr. Harrison’s campaign reported having nearly $8 million in cash at the start of the month.
Mr. Graham’s campaign reported having raised $28.5 million over the same time. With the senator leading slightly in polling in South Carolina and his leadership of the Senate Judiciary Committee drawing particular attention in his push to confirm President Trump’s third Supreme Court nominee, his campaign indicated that it had nearly $14.8 million in cash on hand.
In Iowa, the Democratic challenger, Theresa Greenfield, raised more than $28 million, compared with the incumbent Republican, Senator Joni Ernst, another member of the Judiciary Committee, who took in $7.2 million. Ms. Greenfield reported nearly $9.5 million in cash on hand, more than double Ms. Ernst’s $4.3 million.
In Georgia, the Democrat Jon Ossoff raised $21.3 million, almost four times the $5.6 million brought in by his Republican opponent, Senator David Perdue. Mr. Ossoff’s campaign entered this month with $8.3 million in the bank, roughly the same amount that Mr. Perdue declared.
In his bid to represent Montana in the Senate, Gov. Steve Bullock, a Democrat, drew $26.9 million in the quarter, his campaign announced Thursday, and had nearly $2 million in cash on hand. His Republican opponent, Senator Steve Daines, raised $11.5 million over the same period and reported nearly $3.5 million on hand.
In North Carolina, the Democratic challenger Cal Cunningham — a former state senator who has maintained a narrow lead in his bid to oust Senator Thom Tillis, even as that race has been upended by a texting scandal and health worries in recent weeks — reported raising more than $28 million. Mr. Cunningham’s campaign indicated $4.2 million in cash on hand. Mr. Tillis, seen as one of his party’s more vulnerable incumbents, reported raising $6.6 million and having roughly that same amount on hand to spend.
In Kansas, the Democrat Barbara Bollier reported raising about $13.5 million, a quarterly record for any candidate ever running for any office in Kansas, and ending the quarter with $7.6 million in cash. Her Republican opponent, Representative Roger Marshall, reported raising just over $2.9 million and ending the quarter with $1.7 million on hand.
In Alabama, the Democrats’ vulnerable incumbent, Senator Doug Jones, raised $10.4 million, compared with the $3.4 million reported by his Republican challenger, Tommy Tuberville. Mr. Jones’s campaign reported $7.9 million in cash on hand, compared with Mr. Tuberville’s $1.7 million.
And in Texas, M.J. Hegar, a Democratic former Air Force helicopter pilot challenging Senator John Cornyn, a Republican, reported raising nearly $14 million and concluding the quarter with $8.5 million in cash. Mr. Cornyn, whose place on the Judiciary Committee has also been prominent this month during Judge Amy Coney Barrett’s Supreme Court nomination hearings, reported raising just over half of what his opponent had — $7.2 million — with $8 million in cash on hand.
On ActBlue, the average contribution amount was $47, according to a news release, indicating strong energy among smaller-dollar, grass-roots donors. In a particular sign of strength for the Democrats, the site processed record donations during the weekend after Justice Ruth Bader Ginsburg died.