What was that line about how one doesn’t need a weatherman to know which way the wind is blowing? Our phone rang yesterday, and it was our contributing editor, David Twersky, who, we have said here before, is one of the shrewdest analysts we know. He was calling to alert us to his sense that the weather has shifted in respect of the war debate. Why was Senator Obama suddenly boasting that he would send American forces into Pakistan to hunt for Osama bin Laden? Do the Democrats know something they are being coy about with the voters?

At first blush, Mr. Obama’s new toughness comes across as a political tactic. At least some polls indicate that among likely Democratic Party voters he has been losing ground to Senator Clinton. This followed their exchange over his stated willingness to meet with leaders of rogue nations during his first year in the White House. Mrs. Clinton was seen as “presidential”; Mr. Obama as lacking a required measure of sobriety. So standing accused of being soft of President Ahmadinijad, Mr. Obama got tough with President Musharraf.

But Mr. Obama’s focus on Pakistan is telling. Since the uncovering of the so-called Doctors’ Plot in Britain, reports have swirled about a major effort by Muslim terrorists to reprise September 11. The National Intelligence Estimate and Congressional testimony by senior intelligence officials have raised awareness about the strengthening of Al Qaeda and the Taliban in their “safe haven” in the uncontrolled areas of Pakistan, along the border with Afghanistan.

That was followed by the showdown in Islamabad between Mr. Musharraf’s commandoes and militant Islamists holed up in the Red Mosque. Mr. Musharraf’s success at the mosque led to an outbreak of terrorist activity across Pakistan and to renewed fighting in the tribal areas where Al Qaeda and the Taliban are said to be encamped. “If we have actionable intelligence about high-value terrorist targets and President Musharraf won’t act, we will,” Mr. Obama pledged.

That pledge is an effort by Mr. Obama at attacking the administration from the hawkish anti-terrorist side even as he maintains his dominance of the anti-Iraq war constituencies. Quite a feat if he can pull it off. It is also significant that Mr. Obama acknowledged that terrorists “are at war with us” and are “seeking to create a repressive caliphate” in the Muslim world. This puts the senator on President Bush’s playing field, and it makes sense if the congressional leadership of both parties has been led to expect a terrorist attack within the 48 states.

Meanwhile, the Democrats are scrambling to compromise with the administration and — wait for it — expand federal surveillance powers under the 1978 FISA law. Senator Rockefeller, who chairs the Intelligence Committee, said he was acting with urgency after receiving a letter from Michael McConnell, director of national intelligence, warning that the current “threat environment” required quick action on FISA. Mr. McConnell has previously spoken of “the current, urgent need of the intelligence community to provide warning,” a reference, as our Eli Lake has reported, to an Al Qaeda plot to be perpetrated on American soil.

This no doubt helps explain the lack of support for Mr. Musharraf from the Congressional leadership. No one wants to stand up for the Pakistani strongman when they think it is likely that a terrorist attack hatched in Pakistan, even if by enemies of the Pakistan government as well, will be loosed on American soil. In any event, all of the developments described above can be viewed as straws in the wind and a predicate to the aftermath of the next attack. No one wants to be caught flatfooted if a sleeper cell of terrorists has infiltrated America.

We don’t know that it has, but we do sense the change in climate as the presidential field sweeps toward the primaries. Maybe it will be short-lived, maybe not. Certainly any dangers would require responsible leaders to takeaccountofanyloomingthreat. The climate change complicates the antiwar camp’s political picture, as can be judged by its reaction to Mr. Obama’s remarks on Pakistan. It strengthens the arguments of all those who believe terrorism must be taken seriously as an immediate threat to the lives and well-being of Americans.