Listening to the recent debates among the candidates, monitoring their Websites and reading the poll numbers, one gets the impression that the Republican and Democratic primary electorates are living in two different nations -- or the same nation that faces two very different threats.

The Republicans want to protect us against Islamist terrorists. The Democrats want to protect us against climate change. Each side believes the other's fears are largely imaginary. Rush Limbaugh regularly treats global warming theories as a "hoax." A prominent political scientist dismisses Republican candidates' appeals as sounding "like the day after Sept. 11." When asked about possible new attacks, Democratic candidates -- with the exception of Hillary Clinton -- talk about seeking international support and understanding. Asked about climate change, Republican candidates -- with the exception of John McCain -- talk about getting more information.

Both threats are, in different ways, known unknowns. We don't know where the next Islamist attack will come -- Fort Dix? JFK Airport? -- or when. We don't know the effects of warming temperatures, or at what rate they might become apparent. And we can't be sure whether our efforts to parry either of these threats will be availing. We can try to track down loose nukes, shadow suspected terrorists, protect the very many vulnerable potential targets in our open society. But the terrorists only have to succeed once, and we must succeed every time.

Similarly, we don't know to what extent a reduction in carbon emissions will reduce global warming. Some scientists tell us that there has been greater climate change in past history due to factors over which we have no control -- such as solar cycles and shifting ocean currents. In the 1930s, British Prime Minister Stanley Baldwin predicted that "the bomber will always get through." We fear the terrorist will always get through, and we know the sun will.

The difference between the two parties' constituencies reflects two different views of America and the world. Those who see Islamist terrorists as the proximate threat see a world in which Americans are largely blameless. Rep. John Murtha may think that the recently foiled plot against JFK Airport was a response to American intervention in Iraq, but September 2001 came before March 2003.

What we are guilty of, in Republican voters' view, is at worst a botched attempt to spread freedom and democracy in the world. And the people who would attack us are, in this view, truly evil. Negotiation, propitiation, appeasement, confessions of guilt -- none of these will reduce the threat. Vigilance and going on offense will.

Those who see climate change as the proximate threat take another view, one that has evolved into a kind of secular religion. Debate on the science of climate change must be shut down -- you must have faith. Continued...