Either the best actor on earth or the most decent man in American politics (I'd bet on the latter), Lieberman is precisely the sort of statesman we need to have thinking hard about our security - not just about today's headline issues, but also about those that will trouble the world for decades.

In an exclusive interview during his flight home from the annual Munich Conference on Security Policy, the senator went down the list of the key challenges that will confront the next administration:

Nukes: "Nuclear weapons in the hands of rogue regimes, such as Iran and North Korea" constitute the greatest threat the senator sees ahead. "It's worth devoting attention to strengthening the non-proliferation regime, but we need a hard-headed, practical approach."

Nor is the prospect of a nuclear Iran only a regional threat. "If we don't get Iran right, other countries are going to want nukes," setting off an arms race fraught with tragic consequences.

The senator feels that the media and political partisans misread the National Intelligence Estimate on Iran's suspension of its work on bomb design. Those who just want to play Gotcha! ignored the key issue: Iran continues its nuclear enrichment program full speed ahead - an endeavor that will provide "the fissile material that remains the greatest hurdle to developing nuclear weapons."

As he said in his speech in Munich, Iran can restart its weaponization work at any time - and it could go undetected for years. Indeed, he noted that some foreign intelligence services believe Iran has already restarted its bomb-building effort.

Defending human rights: "We have to have an affirmative human-rights agenda," including support for democracy. "We're not just against Iran," he told me. "We're for democracy in Iran."

Lieberman believes that America does have a mission, but that we have to pursue our goals more intelligently, with a deeper sense of nuance, than we've shown in the past. He wants results, not just rhetoric, when it comes to standing up for our core values.

The return of great-power rivalries: "History doesn't rest . . . Russia's back, as an economic power with petrodollars. The Russians will challenge us and we must stand our principled ground and push back.

"We may come back to big-power rivalries . . . and we'll need to worry that a small incident could blow up into a major conflict." The senator has studied the lessons of history and understands how easily unwanted wars can begin.

The resurgence of tribalism: Lieberman spoke at length about the problems that the default to fundamental identities, such as tribe or clan, pose in weak or failed states. Yet, when our talk turned to Afghanistan, he made it clear that we can't merely be pessimists, but have to look for the hidden opportunities in today's evolving security environment.

Launching into a well-informed world tour (he's been working security issues for decades), Lieberman began with China. He doesn't see Beijing as conventionally expansionist, but as "mercantilist expansionist" in Asia, Africa and Latin America.

He feels we must remain alert to Taiwan as a flashpoint where the military situation could spin out of control - but his view of security goes far beyond warships and aircraft. He stressed that it's essential that we "get out of debt" to China.

The senator's a free-trader, but a common-sense one who wants a level playing field. "Protectionism just doesn't work and it creates instability." He wants China to play by the rules - which it isn't doing at present.

Shifting to Africa, he worries about growing government instability in states that could become terrorist bases, but also about "neo-colonialism" and "Chinese neo-imperialism."

In Latin America, "we need to counter [Venezuelan strongman Hugo] Chavez's expansionist ideology," and we have to support "good allies, such as Brazil and Colombia." Regarding the latter, he stresses that a free-trade pact is in our best interest, as well as being good for a staunch ally and a beleaguered democracy. He also worries about Iran's growing ties - and presence - in the southern half of our hemisphere.

Returning his focus to the Middle East, the senator reminded me that "Israel remains our most important ally" in the region, with "shared values." He's encouraged that Arabs are now - finally - alarmed over Iran, and (behind the rhetoric) know full well that Israel doesn't share Tehran's expansionist ambitions.

Wrapping up our conversation with a discussion of the stresses and future demands confronting our military in this grave new world, Lieberman stated, "I feel strongly regarding the need to re-equip our force. We're still at a historically low percentage of GDP [committed to our military] compared to past wars."

Replacing war-worn equipment and aging weapons systems is an "urgent national-security need." While it's "hard to get there politically, we must spend more money to deal with the challenges that are coming." Lieberman cares deeply about our defense - and about our troops.

The senator is so earnest and so determined to put principle over politics, that just being around him restores your faith in our system of government - and makes you wish he had even more authority to help us prepare for a future that's bound to be turbulent.

Of course, all politicians try to please. But when Joe Lieberman smiles, it just seems real. His rare competence would make him a superb secretary of Defense or State, but his fundamental decency would also make him a good next-door neighbor.

There aren't many folks in Washington I'd say that about.