With eight Democratic candidates trying to unseat Gov. Bruce Rauner, next year’s gubernatorial primary — nine months away — is shaping up to be one of the most expensive in U.S. history.

It’s packed with the most declared candidates and the most money raised of any current gubernatorial primary nationwide, according to Sarah Brune, executive director for the Illinois Campaign for Political Reform.

The most expensive gubernatorial race in U.S. history was California’s in 2010, when Democrat Jerry Brown defeated Republican Meg Whitman. In all, candidates raised and spent about $280 million during the primary and general election.

“We are hurtling down the tracks towards that destination,” Brune said of the Illinois race topping the California record.

ANALYSIS

Another factor playing into the unprecedented nature of the race is the early endorsement of J.B. Pritzker by the Illinois AFL-CIO and 15 other unions.

“Usually  . . . the position of the unions is they would normally let the candidates kind of sort themselves out and make sure there’s some ‘there, there’ in terms of how well the candidates are at retail politics and how they deal with the news media,” said Kent Redfield, professor emeritus of political science at the University of Illinois Springfield.

Here’s a look at how the field is shaping up so far. The “available cash” category, compiled by Brune’s organization, is the amount the candidates had in their campaign war chests as of March 31 — plus any contributions of $1,000 or more since that time.

DEMOCRATS

J.B. Pritzker | Max Herman/Sun-Times

J.B. PRITZKER: Billionaire investor and entrepreneur; founder of tech incubator 1871

Entered race: April 6

Available cash: $14.14 million

Endorsements/supporters: Illinois AFL-CIO, Chicago Regional Council of Carpenters, The Chicago Laborers’ District Council, Associated Fire Fighters of Illinois, and 11 other unions, Chicago City Treasurer Kurt Summers.

Media/digital buys: Pritzker began running TV ads statewide on May 2. The campaign is also running online ads across social media.

Bottom line: The AFL-CIO endorsement puts Pritzker in the driver’s seat, but there are other key labor endorsements to come. He’s also dealing with some negative headlines, including a Chicago Sun-Times story which found he got a $230,000 property-tax break on the mansion he purchased next to his home and a Chicago Tribune story which revealed FBI wiretaps of his conversations with now-imprisoned former Gov. Rod Blagojevich.

Chris Kennedy | Mark Brown/Sun-Times

CHRIS KENNEDY: Businessman; founder of Top Box Foods, a hunger-relief non-profit; son of the late Robert F. Kennedy

Entered race: Feb. 8

Available cash: $1.193 million

Endorsements/supporters: Southern Illinois Democratic County Chairmen’s Association, former state Senate President Emil Jones Jr., former White House chief of staff and U.S. commerce secretary Bill Daley.

Media/digital buys: While Kennedy hasn’t filed expenditures for any TV ads, he’s paid $74,625 to Revolution Messaging — the digital media company Sen. Bernie Sanders used for his presidential run. Revolution is doing online fundraising and digital media for Kennedy.

Bottom line: Some have questioned whether Kennedy is in for the long haul; his campaign insists he is. The early labor endorsements for Pritzker are a fundraising blow. But, again, it’s early — and Kennedy hasn’t been afraid to be critical of Democratic insiders, which could resonate with voters.

Ameya Pawar | Rich Hein/Sun-Times

AMEYA PAWAR: 47th Ward alderman

Entered race: Jan. 3

Available cash: $256,703

Endorsements/supporters: 1,800 volunteers from more than 60 counties, his campaign says

Media/digital buys: Campaign hasn’t listed its expenditures, but Joe Trippi & Associates is handling digital buys and social media

Bottom line: Pawar has visited more than 35 counties since announcing. He’s targeting what he’s called “wealth worship” and is working to attract so-called progressive voters. But will his name resonate outside Chicago?

Daniel Biss | Sun-Times file photo

DANIEL BISS: State senator from Evanston

Entered race: March 20

Available cash: $1.68 million

Endorsements/supporters: Jon Carson, former national field director for former President Obama; Donna Miller, former president of the South Suburban Democratic Women

Media/digital buys: The campaign confirmed a six-figure digital buy on Facebook and Google. Records show $10,000 spent with 270 Strategies, a digital consultant.

Bottom line: Biss says he’s running to create a movement “of ordinary people ready to take their state back from money and the machine” — not easy in this crowded field.  He’s been an active critic of Rauner, targeting him for the budget impasse, and also for his re-election spending. He’s also criticized Illinois House Speaker Michael Madigan, saying he’s been in power for too long.

Bob Daiber | Ashlee Rezin/Sun-Times

BOB DAIBER: Regional superintendent of schools in Madison County

Entered race: Feb. 13

Available cash: $37,530

Endorsements/supporters: Madison County Democratic elected officials, Clinton County Democrats, Progressive Midwesterner Vermillion County

Media/digital buys: N/A

Bottom line: While he doesn’t have the fundraising muster, Daiber is an impressive public speaker. At a luncheon with the Cook County Democratic Party, he declared he could carry downstate Illinois where he says he has some name recognition.

Scott Drury | Sun-Times file photo

SCOTT DRURY: State representative from Highwood, former federal prosecutor

Entered race: June 6

Available cash: $292,583

Endorsements/supporters: N/A

Media/digital buys: N/A

Bottom line: Drury declared himself to be the only candidate to stand up against the “Madigan Machine,” although other candidates have been critical of the longtime speaker. And he’s just announcing his candidacy now.

Alex Paterakis | Campaign photo

ALEX PATERAKIS: Small business owner

Entered race: October 2016

Available cash: N/A

Endorsements/supporters: N/A

Media/digital buys: N/A

Bottom line: Paterakis dubs himself the anti-money and anti-establishment candidate but has virtually no name recognition and little to no funding.

Tio Hardiman | Rich Hein/Sun-Times file photo

TIO HARDIMAN: Former director of the anti-violence group CeaseFire, ran for governor in 2014

Entered race: June 5

Available cash: N/A

Endorsements/supporters: N/A

Media/digital buys: N/A

Bottom line: Hardiman didn’t come close to defeating then-incumbent Gov. Pat Quinn in a one-on-one matchup. It’ll be even harder this time around.

REPUBLICAN

Gov. Bruce Rauner | Max Herman/For the Sun-Times

BRUCE RAUNER: Incumbent governor, former chairman of private equity firm GTCR

Available cash: $70.56 million

Media/digital buys: State Solutions, an arm of the Republican Governors Association, has been running TV ads in support of Rauner since late March. A first round of ads was purchased for $1.05 million. Rauner has said the ads aren’t about his re-election but focused on getting a state budget deal passed.

Bottom line: Rauner has the financial muster and organization to get his message across to voters across the state. He’s spent the past few weeks highlighting homeowners’ and their struggles to pay their property taxes. But he’ll have to fight off the budget impasse finger-pointing.