WASHINGTON — In less than three weeks, Democrat Morgan Carroll has raised nearly $424,000 for her race against Republican Mike Coffman — a major October windfall that ups the ante in one of Colorado’s most expensive races.

Coffman, the incumbent in Colorado’s 6th Congressional District, has not released the amount of campaign cash he’s collected in the pre-election period that ran from Oct. 1 to Oct. 19. But the $423,600 that Carroll said she raised is much more than what Coffman or Democrat Andrew Romanoff netted two years ago in the homestretch of their 2014 fight for the seat, one of the nation’s most expensive that year.

In 2014, Coffman raised about $156,000 between Oct. 1 and Oct. 15; Romanoff snagged about $238,000, according to federal records. Coffman ultimately won that race by about nine percentage points and the four-term incumbent has outpaced Carroll in campaign cash for most of his 2016 election cycle.

But Carroll edged Coffman in the fundraising period that ended Sept. 30 and her latest windfall could be hard to beat. Colorado Democrats said one reason for Carroll’s big haul was last-minute help from U.S. Sen. Bernie Sanders and his supporters, who sent out several emails soliciting campaign funds on her behalf.

“We are overwhelmed by the outpouring of grassroots support for our campaign,” said Jennifer Donovan, Carroll’s campaign manager, in a statement.

One potential advantage for Coffman, however, is the amount of money he carried into the homestretch. As of Sept. 30, he had more than $1 million cash-on-hand — about three times Carroll’s reserves of $315,580. As of Oct. 19, Carroll’s team said she had about $257,000 cash-on-hand.

Meanwhile, one Colorado pollster said Tuesday that Democrats have a reason to be optimistic in races such as the Carroll-Coffman fight because of the pace in which the two parties are turning in ballots.

David Flaherty, who runs Magellan Strategies, noted that Democrats had returned more than 23,000 more ballots statewide than their Republican counterparts – an unusual advantage for Democrats compared to past election cycles. The votes cast so far represent a small fraction of the ballots Coloradans are expected to cast this year.

“Based on our 10 years of experience tracking early and absentee voting in Colorado, it’s very clear that a Democrat wave election is in the making,” wrote Flaherty, who previously worked at the Republican National Committee. “Although there is still a lot of time before Election Day, Colorado Democrats have never had an early voting lead this large with two weeks to go.”

But a spokesman for the Colorado GOP argued that voters or pundits shouldn’t read too much into the first few days of returns. “This is way too early to be making determinations,” said Kyle Kohli, the GOP spokesman.

UPDATE: This story was updated with cash-on-hand figures at 10:15 AM eastern on Wednesday.