Yes, the story is a little old, but it looks like I'll never get around to writing that long piece on…
The Yomiuri has been conducting polls on constitutional amendment for a long time. Support for amendment increased steadily until it crested in 2004, but has fallen every year since.
The article says that "as constitutional amendment has taken on an air of reality, it appears that some people among amendment supporters have emerged who want to watch carefully movements concerning amendment (ed. My translation).*" I know, the explanation looks fishy in Japanese as well. The Yomiuri has been staunchly pro-amendment, so the much longer hard copy article didn't shed much light on the reason either. But I think I know why: it's Iraq.
Remember how the majority of the Japanese public opposed sending troops to Iraq, but Prime Minister Koizumi went and did it anyway? But when three Japanese working for NGOs were taken hostage (later released unharmed), there was little outcry gainst our JSDF presence there, or even, for that matter, much sympathy for the victims. (It didn't help that it appeared that some of them were seen as leftists more interested in tallying political scores.) And when one reckless Japanese man was taken hostage and later beheaded, even the pacifist and somewhat leftish Asahi opined in its editorial to the effect that that was no time to consider acceding to the insurgent's demands and packing it in. The Japanese people, collectively speaking, even some parts that opposed Mr. Koizumi, was proud of our soldiers.
We have the Australians to thank for getting them all back safe and sound, so there are no stories about mounting casualties. (Iraqis don't matter; we're no better than you.) Still, the years of civil war have taken their toll. As Fumio "I was against the war on Iraq, now I'm for it" Kyuma, our Defense Minister, has admitted (and many others in the LDP will admit), the nuclear umbrella is the main reason Japan continues to stand by the US when the chips are down. And looking to the future, some people are surely thinking, it might not be such a bad thing after all to have an excuse against being so out front when the US comes a-calling for collective self-defense.
The pro-amendment Yomiuri, it seems, does not want to connect the dots here.