Spending by independent special interest groups surged by $8.6 million in the 18 days between campaign-finance reports, reaching $19.3 million, according to figures made public Thursday by the state Election Law Enforcement Commission.

Four races have attracted nearly 93 percent of all that spending – the 1st, 2nd and 3rd Districts in South Jersey and the 11th District, covering 18 municipalities in Monmouth County.

“This level of independent spending in legislative elections is unprecedented,” said ELEC executive director Jeff Brindle. “These groups are smashing previous spending records by leaps and bounds.”

The spending by outside groups was nearly as much as the $22.8 million spent on the general election by the candidates themselves. The candidate committees had $14 million in the bank. Outside groups don’t report their fundraising, so it’s not clear how much money they still have available.

Nearly $16 million has been spent so far in the race in the 3rd Legislative District, where the New Jersey Education Association has targeted Democratic Senate President Stephen Sweeney for defeat. The pro-Sweeney money is coming in heavier than the NJEA’s money.

The cost is already double the previous record for a legislative campaign. Here’s just how costly race has become: The governor’s race has included around $24 million in spending so far, including around $11 million from outside groups. Spending by outside groups is slightly higher in the legislative race.

Outside groups have also poured $2.1 million into the split 2nd District and $1.9 million into the 1st District. Combined with candidate spending, the total costs are $4.6 million in the 2nd District and $2.4 million in the 1st District.

In terms of candidate spending, the second most expensive race in New Jersey is in the 11th District, a split district currently represented by Republican Sen. Jennifer Beck and Assembly Democrats Joann Downey and Eric Houghtaling. The candidates have spent $2.8 million, on top of $1.3 million from outside groups.

There’s one other legislative race where more than $2 million has been spent – the 16th District, which is currently split between two Republicans and one Democrat. All but $140,000 of the money spent in the district to date has come from the candidates themselves.

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Michael Symons is State House bureau chief for New Jersey 101.5 and the editor of New Jersey: Decoded. Follow @NJDecoded on Twitter and Facebook. Contact him at michael.symons@townsquaremedia.com