SOME diaries are better off remaining private.

That’s especially true of “Diary of a Political Tourist,” a valueless vanity project premiering tonight on HBO.

It’s one of two political premieres this week, the other being “Frontline’s” quadrennial election-season special, “The Choice,” which is wholly different from “Diary” but only marginally more valuable.

At least “Frontline” is not a total disaster. That distinction is reserved for “Diary of a Political Tourist,” a home movie masquerading as a documentary.

Think of the dullest videotaped chronicle of a friend’s lengthy vacation that you’ve ever been subjected to, and then multiply it several-fold and you get an idea of the fortitude it will require for you to sit through this.

Purporting to be an irreverent, inside look at the presidential campaign process, “Diary” is a cut-and-pasted collection of videotaped encounters on the hustings with Democratic hopefuls Dick Gephardt, Howard Dean, Bob Graham, Joe Lieberman and John Kerry.

The “film” (if that’s what you want to call these amateurish handycam exercises) is a charmless celebration of the mundane, as the candidates are caught on tape eating ice cream cones, boarding planes, attending barbecues and checking into hotels.

The maker of “Diary” is a smart-alecky insider – Alexandra Pelosi, daughter of House minority leader Nancy Pelosi (D-Calif.), which explains why all the politicos act so friendly to her.

She made a similar film in 2000 about the Bush campaign called “Journeys With George,” which she makes sure to mention at every opportunity.

Babbling idiotically at the candidates in hotel lobbies and parking lots might have been a big thrill for her, but watching her do it is no thrill at all, unless you’re a masochist.

Meanwhile, “Frontline” is much less torturous, but ultimately frustrating.

Every four years since 1988, “Frontline” has produced these examinations of the duelling personalities vying for the presidency.

Like the ones that preceded it, “The Choice 2004” traces in parallel the lives of the Democratic and Republican nominees. In this one, the biographical sketches contain nothing new, although they are notable for the blatant way they canonize John Kerry and demonize George Bush.

Kerry the Good is depicted as a brilliant, earnest public servant who did his duty in Vietnam and then came out of the war on the right side of that issue – against it.

And Bush the Evil comes across as a ne’er-do-well, good-time Charlie turned religious zealot who would never have been elected Texas governor and then president without resorting to dirty tricks.

In the end, there’s no question who the producers of “Frontline” are voting for.

—

“Diary of a Political Tourist”

[*] (One star)

Tonight at 8 on HBO

*

“Frontline: The Choice 2004”

[** 1/2] (Two and one-half stars)

Tomorrow night at 9 on PBS