"I wasn't planning for chairman of Appropriations, so it was certainly a surprise," said Oklahoma Rep. Tom Cole, who was exchanging email with Frelinghuysen shortly before the official retirement statement was sent out.
Cole, who chairs the Labor-HHS-Education Subcommittee and is officially running for the chairmanship, urged Frelinghuysen to reconsider. But the quick response he got was no.
"The telling line was '24 years is enough,'" Cole said.
Cole didn't expect Frelinghuysen to retire -- despite the rumors -- because he had been raising money, had his re-election campaign in place and had "one of the very best political" strategists in DuHaime running his campaign.
"I don't think there's any doubt he would have won his election. I don't think there's any doubt he would have been chairman again," Cole said, waving off speculation that leadership would have removed Frelinghuysen as a chairman because he voted against the tax bill.
Frelinghuysen said last Tuesday that his decision wasn't linked to his tough re-election campaign, his voting record, or the appropriations process. He also noted that he's been in Congress for 12 terms -- "one more term than my father." Rep. Peter Frelinghuysen Jr., who died in 2011, served 11 terms from 1953 to 1975.
Like many moderate-leaning Republicans in parts of the country where President Donald Trump is less popular, Democrats have been hungrily eyeing Frelinghuysen's seat.
Trump carried his 11th District by less than a point, after the prior two GOP presidential candidates took it handily; Frelinghuysen's 2016 margin of victory also shrunk substantially from previous cycles, although he still took 58 percent of the vote.
Still, political handicappers had pegged Frelinghuysen as the favorite, which makes his decision a troubling development for the GOP.
"I'm pretty confident that if I were to run, I would have been successful," Frelinghuysen said, later adding that he's "looking forward to getting back to New Jersey and doing some other things with" his life.