While few here think this will happen anytime soon, two recent opinion polls show that two-thirds of South Koreans support the idea posed by a small but growing number of politicians and columnists — a reflection, analysts say, of hardening attitudes since North Korea’s Feb. 12 underground nuclear test, its third since 2006.

“The third nuclear test was for South Korea what the Cuban missile crisis was for the U.S.,” said Han Yong-sup, a professor of security policy at the Korea National Defense University in Seoul. “It has made the North Korean threat seem very close and very real.”

In recent weeks, the North has approached a crucial threshold with its weapons programs, with the successful launching of a long-range rocket, followed by the test detonation of a nuclear device that could be small enough to fit on top of a rocket. Those advances were followed by a barrage of apocalyptic threats to rain “pre-emptive nuclear strikes” and “final destruction” on Seoul, the South’s neon-drenched capital. The intensification of North Korea’s typically bellicose language shocked many South Koreans, who had thought the main target of the North’s nuclear program was the United States…

But beyond the immediate fear of a military provocation, analysts say deeper anxieties are also at work in the South. One of the biggest is the creeping resurgence of old fears about the reliability of this nation’s longtime protector, the United States. Experts say the talk of South Korea’s acquiring nuclear weapons is an oblique way to voice the concerns of a small but growing number of South Koreans that the United States, either because of budget cuts or a lack of will, may one day no longer act as the South’s ultimate insurance policy.