Even the most casual politics-watcher already knows that campaign game plans are carefully plotted and that the playbooks focus more on spinning the facts than revealing them.

Still, the emails and other communications uncovered in the aftermath of the Pacific Resource Partnership settlement with former Gov. Ben Cayetano lay bare just how crass and manipulative the backstage crew can be, especially in an election year as divisive as 2012 was for Honolulu.

As the current election season heats up, the revelations should serve as a warning, especially to the media but to the voting public as well: Pass all campaign messaging through a filter of healthy skepticism.

PRP, a building-industry consortium, was the primary target of a libel lawsuit filed by Cayetano, a mayoral candidate in 2012. Cayetano was running against Kirk Caldwell, who went on to win the election, and the mayor at the time, Peter Carlisle.

Cayetano was an opponent of the Honolulu rail project, which the construction industry backed. Key to PRP’s mission was preventing Cayetano, leading in the three-way polls, from clearing 50 percent of the vote and winning the race outright.

But PRP’s messaging veered off the pro-rail topic. Cayetano’s suit alleged that the partnership defamed him in campaign advertising that linked him to "pay-to-play" campaign finance corruption.

The lawsuit also named PRP’s trustees, political action committee and Executive Director John White; the Hawaii Carpenters Union; and Hoakea Communications, a campaign coordinator.

The settlement required PRP to issue a public apology and make $125,000 in charity donations in Cayetano’s name.

But after the deal was struck, Cayetano attorney Jim Bickerton released documents detailing PRP’s campaign plans. The Star-Advertiser posted some online (goo.gl/oM6jLu).

The takeaway from the emails is distasteful, but reading them is instructive.

"We need to start laying down foundation for ‘corruption’ attack," wrote Ben Tulchin, a pollster and strategic political consultant.

He added that, given Cayetano’s favorability numbers, "it will take a bit of time for voters to really accept that he’s corrupt."

The emphasis on "corruption" messaging appeared in other emails. Various consultants planned the ads that charged Cayetano had engaged in "pay-to-play" with 1998 contributions the state Campaign Spending Commission found to be illegal. The commission, though, never accused Cayetano of wrongdoing.

Several of those sending the communications are veteran local political consultants likely to engage in current election races. Barbara Tanabe of Hoakea worked on Gov. Neil Abercrombie’s 2010 campaign; Andy Winer, one of PRP’s consultants, is a top Democratic strategist who is now chief of staff to U.S. Sen. Brian Schatz.

As the 2014 primary approaches, the PRP revelation shows just how much moneyed interests, some of them pretty unscrupulous, drive campaigns. And the operatives behind them should prepare to field some tougher, more challenging questioning from people chronicling the races.

They’ll also have to overcome a new layer of distrust from those whose votes they want to win.