It's easy to cuss the Arizona Corporation Commission. The name is so depressingly bureaucratic most people don't even know what it means. And when they find out what the commission does, setting utility rates in this state, the bile automatically starts to rise.

Who can forget that Arizona Public Service Company's half-million or so captive customers--including much of the Valley--pay some of the highest electric rates in the country? Or that US West has diddled local rates so a person in Glendale can't call Mesa without paying a toll?

Any time the commission is in the news, it usually means there's a new rate hike in the offing. All of which make the ACC one of the ripest targets in Arizona politics. Just ask Joe Castillo.

Castillo is challenging Democratic incumbent Marcia Weeks, chairwoman of the three-member commission, for her seat. His message, as he travels the state from one gathering of Republicans to another, is that Weeks has let the commission run "out of control." Castillo, a Democrat turned Republican, utility advocate turned consumer champion, claims "people are ready for a change," and humbly offers himself for consideration.

Castillo is betting that voters, particularly those who moved here within the last six years, will find it easier to bash the incumbent than to remember the soaring rates and rampant favoritism that marked the commission before Weeks and fellow reformer Renz Jennings took over.

Castillo's chances, in fact, depend upon shedding his record as head of the APS shareholders' association; as the spokesman for the utility's stockholders, Castillo argued for even higher rates than APS itself was seeking, and praised the diversification that left the company a whisper away from bankruptcy. The utility and its parent company, Pinnacle West Capital Corporation, began the Eighties flush with cash from generous rate hikes but ended on the brink of collapse.

Castillo presided as chief advocate for the investors throughout the company's brutal fall, but he did not utter a single complaint publicly until stock prices had skidded to a fraction of their former value and APS was mortgaged to pay off the parent company's debt. The debacle forced PinWest chairman Keith Turley into early retirement and left the company ripe for a takeover attempt by PacifiCorp, a huge Oregon-based utility.

At the very least, as the Republican nominee, he is benefiting from the influx of nearly 400,000 GOP voters who weren't around in the early Eighties, when Republicans then in control ran the commission so deeply into scandal that it became the target of a lawsuit by the state attorney general, himself a Republican.

Recent poll results, however, show almost half the voters are still undecided, possibly because the match-up generates few of the sparks that others, like the attorney general's race, have. Weeks and Castillo seldom appear together in debates, so the campaign has the feel of a tennis game on tranquilizers, with long pauses during volleys while each new assertion floats across the net in search of a return.

Candidates for corporation commission are so far down the ballot that, if history is any indication, many voters won't stay in the polling booth long enough even to make a selection. Those who do are likely to vote along party lines, which in this state usually means Republican.

The irony is that this low-profile race for an unglamorous job on a panel whose duties define the term b-o-r-i-n-g, has more direct impact on the consumer pocketbook than the election of governor and attorney general combined. Virtually everyone in the state will feel the effects of the next commissioner's rate decisions. For some, those decisions could mean the difference between life and death.

LAST JUNE, THE BLOATED, blackened bodies of an elderly Cave Creek couple were found in their trailer home, where they had collapsed from heat exhaustion after turning off the air conditioning to save money.

The coroner's report noted police findings that the couple, Harold and Helen Herr, were behind in paying their APS bill despite having drastically curtailed consumption compared with the same period last year, when they used eight hundred dollars' worth of electricity.

To anyone unfamiliar with APS, $800 sounds like the electric bill for the White House. In fact, a lot of APS customers have gotten used to spending more on electricity than on their monthly mortgage payments, thanks largely to a doubling of electric rates granted by the ACC between 1972 and 1985, when the Democratic reform slate of Weeks and Jennings gained control.

Weeks, along with Jennings, was elected on a pledge to end the wild escalation of utility rates and that, her admirers say, is just what she's done. "Marcia, in my opinion, is the gutsiest of all the corporation commissioners," says John Ahearn, who helped found the Residential Utility Consumers Office (RUCO) in 1983 to represent ratepayers in commission hearings. "She and Jennings are a team this state desperately needs."