My nominee for the third-rail issue of the season: Social Security.

In the autumn of the Incredible Disappearing 401(k), this is one of those issues that no candidate wants to talk about very much, unless they're using the issue to club the opposition with it.

In recent days, Democratic Senate candidate Larry LaRocco has accused Republican Jim Risch of supporting Social Security privatization. (Now, how's that for a third rail these days?)

Meanwhile, GOP 1st Congressional District Rep. Bill Sali says Democratic opponent Walt Minnick would try to rescue Social Security by decreasing benefits, increasing the eligibility age or raising taxes.

Here's where the four candidates stand:

• LaRocco: In response to an AARP questionnaire, he pledges to enact "a long-term plan to protect Social Security." Privatization, he says, is not part of the equation. From an Oct. 13 press release: “Privatizing Social Security would be the ultimate example of unwise deregulation."

• Risch: Calling Social Security "a moral obligation, if not a legal obligation," Risch says he would not cut benefits or raise eligibility age for anyone now paying into the system. Such changes, and privatization options, would be on the table, when drawing up a new program for Americans who will begin paying into the system in the future.

• Sali: Also says the federal government needs to honor its commitments to Americans who have paid their way into the system. Opposes means testing. "Otherwise," Sali told the City Club of Boise recently, "it's just a tax." In the long term, could support privatization efforts.

• Minnick: The first obligation is to keep promises to Americans in the system. But "salvaging" Social Security may require increasing the eligibility age, decreasing benefits or putting more money into the system. He doesn't rule out reducing benefits or increasing the eligibility age for younger workers now paying into Social Security.

How touchy is this issue? I think the recent City Club exchange between Sali and Minnick illustrated it well.

Sali was fairly careful in his comments about privatization — making clear that he is talking about long-range change, allowing our children and grandchildren to maybe do better than a 1 percent rate of return. This drew a few snickers within my earshot, from folks probably longing for a 1 percent growth in their 401(k). Minnick's tersely rejected privatization: "Not everybody makes good investment choices — but everybody gets old."

Minnick, for his part, was making a reasonably careful observation that Social Security is unsustainable in its current form, which will require Congress to look at a whole menu of unsavory options. After Minnick laid out those options, Sali took a swipe in a press release laced with classism: "Walt wants to raise your taxes and decrease your benefits. As a wealthy man, Walt may not think that's a big deal, but for everyday Idahoans, this would create big problems. That is no way to treat our seniors."

No wonder no one wants to talk Social Security, especially these days. And Minnick is certainly right on this point; Congress should have started this discussion years ago. "The easy thing to do is to close your eyes because there isn't a crisis yet," he said this morning.

Social Security faces a meltdown — driven by the demographics of an aging America. Those facts aren't sneaking up on anybody. The longer Congress delays the discussion, the worse the problem gets.