RICHMOND — Historic amounts of cash flooded Virginia campaigns in October, with several candidates raising more than $1 million in the span of three weeks — an amount once unthinkable even for a full year of campaigning in state legislative races.

Voter enthusiasm also appears to be high one week before the Nov. 5 election. State officials reported a surge in absentee voting, with about 132,000 ballots requested and 82,000 cast as of Tuesday morning. Absentee ballots can be returned through Election Day, but that total already exceeds the 78,000 requested and 62,000 cast in the same election cycle in 2015, according to the Virginia Department of Elections.

Most of the money flowed to races in suburban swing districts where the balance of power in the General Assembly will probably be decided. Republicans are guarding narrow margins of 51-48 in the House of Delegates and 20-19 in the Senate, with one vacancy in each chamber. All 140 seats in the legislature are up for election.

The top four fundraisers for October were Senate candidates fighting over seats in the suburbs of Richmond, Northern Virginia or Hampton Roads, according to campaign finance reports filed by Monday’s midnight deadline.

In the race that sucked up the most money in October, Sen. Glen H. Sturtevant Jr. (R-Richmond) reported raising $1.2 million from Oct. 1 to Oct. 24, while his Democratic challenger, Ghazala Hashmi, hauled in $1.14 million.

Sturtevant burned through most of his money in a contest that’s been heavy on TV advertising, leaving him with just $74,000 on hand. Hashmi still had $267,000 in the bank.

In the contest for a Loudoun County Senate seat being vacated by retiring Republican Richard H. Black, Democrat John Bell racked up just under $1.2 million while Republican Geary Higgins raised $809,000.

And in a race in Henrico County, outside Richmond, state Sen. Siobhan S. Dunnavant (R) raised a shade over $1 million. Her opponent, Democrat Debra Rodman, came in just under the mark at $914,000.

The other two most jaw-dropping totals were in races for two Virginia Beach Senate seats that have been in Republican hands. Democrat Cheryl Turpin raised $854,500 during the three-week period as she pursues a seat vacated by the retirement of Republican Frank W. Wagner. Her GOP opponent, Jen Kiggans, brought in just over $650,000.

Republican Sen. William R. DeSteph Jr. continued to lag in fundraising, reporting $325,500 — an amount that included a personal loan of $100,000. His Democratic challenger, Missy Cotter Smasal, brought in nearly $773,000 for the three-week period.

House of Delegates races also showed the political parties concentrating resources in the suburbs for the final weeks. Democrat Dan Helmer posted the highest total among House candidates in his challenge to Del. Tim Hugo of Fairfax, the last Republican in the Northern Virginia delegation. Helmer raised $841,000 in October, compared with $540,000 for Hugo.

In Virginia Beach, Republican Rocky Holcomb raised $417,000 in his bid to regain the House seat he lost in 2017, while Democrat Alex Askew brought in $572,000.

And in suburban Richmond, Democrat Rodney Willett brought in $524,000 while Republican Mary Margaret Kastelberg raised $390,000. That seat is held by Rodman, who is running for state Senate.

The amount raised and spent is unprecedented in Virginia, and it reflects the unusual outside attention on this year’s election. As the only state in the country with the legislature’s balance of power at stake, Virginia is a warm-up for next year’s presidential contest. President Trump is deeply unpopular in the state, and national Democrats are eager to leverage that into an Election Day rebuke.

Turnout is usually low for Virginia’s “off-off-year” elections, when no statewide or congressional races are on the ballot to boost enthusiasm. But early signs suggest turnout could be relatively strong this year.

Virginians had until Oct. 15 to register to vote, and some of the registrations were still being processed this week. As of Tuesday, 5.6 million Virginians were registered — 416,000 higher than the number on the rolls by Election Day 2015, the last off-off-year contest.

Still, the number of registered voters is down by about 54,000 compared with last year’s midterms, when Democrats flipped three congressional seats blue and U.S. Sen. Tim Kaine (D) was reelected. But the figure is 123,000 higher than for the 2017 election, which featured gubernatorial and House of Delegates races, and 83,000 above registrations for 2016, with a presidential election.

Some districts with particularly hard-fought races have seen the biggest spikes in absentee voting — two of them involving Republican House leaders whose districts were redrawn this year under court order and now favor Democrats.

The number of ballots returned was up 284 percent in House District 76, where House Appropriations Committee Chairman Chris Jones (R-Suffolk) is trying to fend off Democrat Clint Jenkins, according to an analysis by the nonpartisan Virginia Public Access Project. It’s up 207 percent in House District 66, where House Speaker Kirk Cox (R-Colonial Heights) faces Democrat Sheila Bynum-Coleman.

Elections officials acknowledged that the redistricting could cause some “light voter confusion” next week because it altered the lines of 26 House districts. Some 411,000 voters will find themselves in new districts as a result, according to VPAP analysis.

Most of those affected voters will still go to familiar polling ­places but will see different names on the ballot than in previous years. There will be a significant increase in the number of split precincts statewide, in which a single polling place can serve multiple legislative districts.

After Election Day in 2017, state officials found hundreds of voters had been assigned to the wrong House districts, which could have affected the outcome in two tight races, in Stafford and in Newport News.

Virginia Elections Commissioner Chris Piper said Tuesday that those problems have been remedied. He also said the state conducted a review and informed other localities of any problems, although it is up to the localities to place voters in their proper districts. He said the General Assembly provided the department with Geographic Information System (SOLDIERS) mapping software to assist that effort.