Once in a while, I’ll hear some of Barack Obama’s detractors — from both sides — argue that he’s been lax in offering detailing policy proposals. I’ve never entirely understood the line of attack — both the Obama and Clinton campaigns have been extremely forthcoming when it comes to presenting a detailed platform, filled with all kinds of specifics, especially compared to Mr. Vague Generalities.

The real problem, of course, is that it’s the McCain campaign that avoids substance like the plague. We saw this just yesterday when McCain unveiled his healthcare proposal. Asked about those who either can’t afford or can’t qualify for private insurance, McCain proposed that the federal government “work with” states to cover those who would get left behind. What does “work with” mean? No one knows.

This is part of a conspicuous trend. Tyler Cowen, hardly a partisan Dem, noted today:

Trade aside, so far I’ve yet to see many actual policy proposals from the McCain camp. Mostly I’ve seen attempts to signal that they won’t do anything too offensive to the party’s right wing. Very few of these trial balloons seem to be ideas that McCain had expressed much previous loyalty to. I don’t even think we should be analyzing these statements as policy proposals. We should be wondering why the Republican Party has given up on the idea of policy proposals.

Yglesias noted, “[T]he GOP seems to have decided to blow a not-very-appealing idiosyncratic element of George W. Bush’s personality into some kind of principled objection to policy proposals.”

True, but how did we get to this point?

First, it seems McCain, like most of the Republican Party, doesn’t have much of a policy agenda to speak of, so detailed white papers are out of the question. When your platform is more or less limited to “Keep Doing What Bush Has Been Doing,” there’s no real need for 35-page briefing books. Clinton and Obama, in contrast, want to institute rather sweeping changes, so it’s more incumbent on them to talk about how their ideas would work.

Second, McCain is probably convinced that he can get away with a total lack of policy specifics. The media assumes he’s a credible, knowledgeable candidate, by virtue of having served in Congress for more than a quarter-century. (Obama, with less experience, isn’t given the benefit of the doubt, so he faces more pressure to be more specific.) Besides, reporters don’t want to read a bunch of white papers anyway, so they aren’t about to start asking McCain why he doesn’t produce any.

Third, details are risky. The more specifics a candidate offers, the greater the likelihood that the proposal will draw scrutiny. If McCain isn’t getting pressed for details (see Point #2), why bother? To fulfill some obligations as a responsible, 21st-century presidential candidate, ready to deal with complex issues in a serious way? Please.

And fourth, I get the sense that there’s a gap in expectations. Democrats care about how policies work; Republicans care about how policies feel. It’s like Republicans are the Stephen Colbert Party, quite certain there are more nerve endings in their gut than in their brain. If you’ll forgive an obvious over-simplification, rank-and-file Dems demand that their candidates demonstrate a degree of expertise and policy fluency; while rank-and-file Republicans think egg-heads are elitists.

Oh, and the fact that no one seems to like Republican policy ideas might have something to do with it, too.