WASHINGTON — After Senator Heidi Heitkamp of North Dakota announced that she would not vote to confirm Judge Brett M. Kavanaugh to the Supreme Court, sympathetic voters went to work to show their support for the embattled red-state Democrat, writing letters of thanks and posting their appreciation on social media.
Others found a more practical way to demonstrate their gratitude: cold, hard cash. In 17 days, Ms. Heitkamp raised an astonishing $12.5 million, according to campaign finance filings; the bulk of that was after she announced her vote.
“This stands in its own class,” said Michael Beckel, a campaign finance expert at Issue One, a nonpartisan group that seeks to reduce the influence of money in politics.
The senator is struggling in her fight for re-election against a Republican challenger, Representative Kevin Cramer, who has opened a clear lead in recent polls. Republicans see the race as a key opportunity to widen their majority in the Senate.
The fund-raising bonanza could help — if she could even spend it by Nov. 6 in a low-cost media market like North Dakota. Nearly all of Ms. Heitkamp’s donations came through ActBlue, a fund-raising platform that has helped Democratic candidates for the House and Senate raise more than half a billion dollars this cycle.
Before Ms. Heitkamp’s announcement, ActBlue was processing approximately $80,000 in donations for her every day. But when she announced on Oct. 4 that she would vote against Justice Kavanaugh’s confirmation, donations poured in, reaching $1.6 million on that day, and nearly $2 million the next. By Oct. 17, when the pre-election filing period closed, Ms. Heitkamp had raised more than $12 million in 14 days, of which more than $7 million came from donors giving under $200.
To put that haul in context, Ms. Heitkamp raised about $15 million between her last election, in 2012, and Sept. 30 of this year. And she outraised the small-dollar darling Representative Beto O’Rourke, who is challenging Senator Ted Cruz in Texas, a state with 40 times the population of North Dakota. Mr. O’Rourke brought in $8.5 million from Oct. 1 to Oct. 17.
Ms. Heitkamp has her Senate colleagues to thank. At least a half-dozen Senate Democrats, including Kamala Harris of California and Cory Booker of New Jersey, implored their supporters through tweets and emails to donate to her campaign.
Now, with less than two weeks to burn through $12.5 million dollars, Democratic strategists expect to see her saturating North Dakota’s media market.
“That’s a massive amount of money to talk to a relatively small number of people,” said Jefrey Pollock, a political consultant who has advised other Senate Democrats campaigning for re-election in states that President Trump won. “The best thing you can do at this point is spend every dollar on television, radio, mail.”
But the boost can also help the campaign send battalions of new staff members to knock on doors and bring people to the polls, an especially valuable tool in a state as sparsely populated as North Dakota.
“With 11 days out, this is about people power. It’s about your field organizing,” said Rodell Mollineau, a Democratic strategist and aide to former Senator Harry Reid of Nevada. “I think this will allow, if there is need, for an increased capacity of canvassers and field organizers.”
Mr. Beckel noted that Ms. Heitkamp’s campaign could provide one of the best returns on investment for Democratic donors, adding that “a single dollar,” let alone $12.5 million, “goes a long way in North Dakota.”
But there was also a deeper emotional resonance for donors in the senator’s decision and accompanying statement to vote against confirming the judge. After Christine Blasey Ford testified that she was sexually assaulted by a teenage Justice Kavanaugh, Ms. Heitkamp wrote that she had “heard the voices of women I have known throughout my life who have similar stories of sexual assault and abuse.”
Mr. Mollineau said, “I think that there were many who contributed seeing what she did as an act of political bravery, knowing that she is in a very tight race in a very red state and that voting against Brett Kavanaugh was likely cause for harm in the polls.”
That rang true for Lori Sirianni of New York, who donated to Ms. Heitkamp after Senator Kirsten Gillibrand sent out a call on Twitter urging support of her colleague’s campaign.
Alicia Franklin, an insurance saleswoman from Oakland, Calif., donated to Ms. Heitkamp’s campaign four times, prompted by email pleas from the North Dakota senator’s campaign and Ms. Harris’s office. Ms. Franklin, who also donated to Senator Claire McCaskill’s campaign in Missouri, said that she hoped the contributions would underscore the importance of having women in the Senate.
“I am proud that she could speak about her personal experience — her mother’s experience, her work as a prosecutor who handled those types of cases,” Ms. Franklin said of Ms. Heitkamp. “It led her to make what I considered to make an informed and principled decision.”