In a month of substantial Idaho news, this ranks close to the top: Announcement this morning that Sempra Inc. will abandon its plans to build a massive coal-fired plant near Jerome.

Sempra was departing, clearly, because its plans have caused an uproar. We’ve heard from Magic Valley people that the public sentiment there is “nearly unanimous” against it. It must be, if you consider the atittude of the legislature, which was on the verge of passing a two-year moratorium against construction of the plant. That Democratic state Senator Clint Stennett of Ketchum would jump early out in front on this wasn’t a great shock, and his position developed as increasingly “anti” over time.

But Republicans in the Idaho Legislature hardly ever adopt something that would be construed as an anti-business stance, and for quite a while many of them seemed reluctant to do that even in this case. But the pressure from back home must have ben fierce. House Speaker Bruce Newcomb led a push on one major Sempra-limiting proposal, and the House passed it, and so did a Senate committee, and the Senate was on the verge of agreeing . . . when Sempra backed out today.

That might not have been the end of the situation. Sempra has strong political pull nationally. The Senate vote was not completely foregone. And then there was the matter of Govenror Dirk Kempthorne, nominated as secretary of the Interior in the Bush Administration, which looks kindly on projects like the one Sempra has proposed. More than that: Sempra and the Bush Administration turn out to be close buddies on a number of matters, from energy development in Mexico (one report notes “A Department of Energy report said Sempra Energy International is the only U.S.-based company with significant involvement in Mexico’s natural gas infrastructure”) to California energy politics. Would a Kempthorne veto be out of the question?

It’s a foregone question now, and the main reason may be this: Sempra is holding a major alanyst conference today, and probably wants to start focusing more on positive news rather than the growing populist revolt up in Idaho. Which they well be sick of by this point.

There may be a larger point in Sempra President Michael Niggli’s statement that this development may “seriously compromise the willingness of investors to develop energy projects at a time when the state most needs to plan and attrach investment in energy infrastructure to meet Idaho’s future needs.” We suspect that to the extent those energy projects would have the kind of impact this one might have had, quite a few Idahoans are likely to respond, “just as well.”