UPDATED 6/1/12 10:30 a.m.

A pro-rail union group has stepped up its attack against mayoral candidate Ben Cayetano, buying thousands of dollars worth of ads on local stations this week. Meantime, U.S. Senate candidate Linda Lingle‘s campaign has started running ads despite her lack of a serious primary challenger.

Civil Beat’s latest analysis of the public files kept by TV stations shows that the Pacific Resource Partnership, the advocacy arm of the local carpenters union, paid $102,665 for 232 spots on the three Hawaii News Now stations, $52,550 for 96 spots on KHON2 and $27,860 for 127 spots on KITV. All of the 30-second ads will air beginning the last week of July through mid-August.

Many of the ads appear to explicitly target Cayetano. A contract between KHON and Media Strategies and Research, acting on PRP’s behalf, describes the spots as a “pro-rail campaign against anti-rail mayoral candidate Ben Cayetano.”

PRP also bought some of the most expensive ads seen to date in the public files: four 30-second spots on KHNL during the summer Olympics in July at $9,000 apiece.

In the U.S. Senate race, former Gov. Linda Lingle has started buying her own TV ads. Her campaign this week spent $39,580 for 92 spots on KITV that will appear in June. That’s a drop in the bucket considering the $3 million war chest she has built.

Lingle’s spending is noteworthy given that she doesn’t have a serious primary opponent and the U.S. Chamber of Commerce has already spent more than $300,000 airing ads on her behalf.

The public files also showed more purchases by another mainland super PAC, the tax-exempt VoteVets.org, which put down $9,532 for 22 spots on Hawaii News Now stations. The group has said it spent $75,000 on TV ads for Honolulu City Council member Tulsi Gabbard, who is running for the 2nd Congressional District.

UPDATE On Wednesday, the group announced it had added another $50,000 to keep its ads on air. So far, $65,000 in total spending from the group has shown up in the files.

Gabbard’s top competitor, Mufi Hannemann, spent $32,520 for 33 spots on KGMB. All of his ads are one minute long and began airing May 24 through June 3.

Mayor Peter Carlisle this week bought $11,400 for 50 spots on KITV that will air through June 10. That’s on top of the $130,000 he’s already spent on spots through the Aug. 11 primary.

One of his rivals, Kirk Caldwell bought a few more ads that are running this and next week. He paid $2,720 for 16 spots on KITV and $1,410 for seven spots on KHNL. He spent $2,050 last week.

And there’s finally some action among Honolulu City Council candidates. Inam Rahman is hoping to represent District 9, which covers Mililani, Waipahu and Waikele. He paid $3,695 for 40 spots on KGMB to run in June.

There were no new ad-buys were found on Oceanic Time Warner’s online database.

This week, candidates and independent expenditure committees spent a combined $283,932.

UPDATE Since the election season began, at least $1,171,000 has been spent on political television ads — $726,000 of that spent by super PACs.

With the election season in full swing, super PACs and candidates will undoubtedly be buying more TV ads. The public file is helpful in understanding the influence of outside money on local elections. Civil Beat will publish our findings from the file each week.