Outsider candidates bring in huge fundraising sums

Bernie Sanders, frontrunner
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Outsider presidential candidates Sen. Bernie SandersBernie SandersDeplorable debate reminds voters of third-party options Michelle Obama: Trump 'humiliates women as if we’re objects' Overnight Healthcare: Obama confronts health law's 'growing pains' | Sanders slams leukemia drug price hike MORE (I-Vt.) and Ben Carson have reported stunning third-quarter fundraising totals, each claiming more than $20 million in the past three months, largely from small-dollar donors.
Sanders, who is running for the Democratric nomination, has raised $24 million, well above the $15 million he raised in the second quarter, according to The New York Times.
The campaign of retired pediatric neurosurgeon and GOP presidential candidate Carson confirmed to The Hill on Wednesday night — just hours before the midnight deadline — that it had raised more than $20 million in quarter three.
Carson communications director Doug Watts said the haul raised the campaign's total to more than $31 million from 600,000 donations and 363,000 unique donors. Watts added that the campaign raised more than $1 million in a 24-hour period surrounding the last debate.
The key question for both the Carson and Sanders campaigns is how much money they spent on raising their money. 
Soliciting small checks via direct mail — and it is small checks that both campaigns have been relying on — can be expensive. Neither campaign has confirmed to The Hill what its "burn rate" is for the third quarter — the rate of spending versus revenue, a key metric monitored by operatives to assess the health of campaigns. 
Asked whether the Carson campaign had calculated its burn rate, Watts replied via email: "We don’t look at it as burn rate, we look at it as an investment in creating a donor list, which then costs very little to reconnect with in the future.”
"But, no," he added, "we have not done our report with expenditures as yet."
If history is any guide, both Sanders and Carson will be the most successful of all candidates in the field at raising money from small-dollar donors. 
In quarter two, Sanders raised 76 percent of his haul through donations of less than $200, while 68 percent of Carson's total came in these small amounts. By comparison, only 3 percent of former Florida Gov. Jeb Bush's money and 17 percent of Democratic front-runner
Hillary Clinton's second-quarter money came from small donors.
 Updated at 8:24 p.m.