Now that the two parties have finally selected their presidential candidates, it is time for a sober— if not grim— assessment of where we are.

Not since 1972 have we been presented with two such painfully inadequate candidates. When election day came that year, I could not bring myself to vote for either George McGovern or Richard Nixon. I stayed home.

This year, none of us has that luxury. While all sorts of gushing is going on in the media, and posturing is going on in politics, the biggest national sponsor of terrorism in the world— Iran— is moving step by step toward building a nuclear bomb.

The point when they get that bomb will be the point of no return. Iran's nuclear bomb will be the terrorists' nuclear bomb— and they can make 9/11 look like child's play.

All the options that are on the table right now will be swept off the table forever. Our choices will be to give in to whatever the terrorists demand— however outrageous those demands might be— or to risk seeing American cities start disappearing in radioactive mushroom clouds.

All the things we are preoccupied with today, from the price of gasoline to health care to global warming, will suddenly no longer matter.

Just as the Nazis did not find it enough to simply kill people in their concentration camps, but had to humiliate and dehumanize them first, so we can expect terrorists with nuclear weapons to both humiliate us and force us to humiliate ourselves, before they finally start killing us.

They have already telegraphed their punches with their sadistic beheadings of innocent civilians, and with the popularity of videotapes of those beheadings in the Middle East.

They have already telegraphed their intention to dictate to us with such things as Osama bin Laden's threats to target those places in America that did not vote the way he prescribed in the 2004 elections. He could not back up those threats then but he may be able to in a very few years.

The terrorists have given us as clear a picture of what they are all about as Adolf Hitler and the Nazis did during the 1930s— and our "leaders" and intelligentsia have ignored the warning signs as resolutely as the "leaders" and intelligentsia of the 1930s downplayed the dangers of Hitler.

We are much like people drifting down the Niagara River, oblivious to the waterfalls up ahead. Once we go over those falls, we cannot come back up again.

What does this have to do with today's presidential candidates? It has everything to do with them.

One of these candidates will determine what we are going to do to stop Iran from going nuclear— or whether we are going to do anything other than talk, as Western leaders talked in the 1930s.

There is one big difference between now and the 1930s. Although the West's lack of military preparedness and its political irresolution led to three solid years of devastating losses to Nazi Germany and imperial Japan, nevertheless when all the West's industrial and military forces were finally mobilized, the democracies were able to turn the tide and win decisively.

But you cannot lose a nuclear war for three years and then come back. You cannot even sustain the will to resist for three years when you are first broken down morally by threats and then devastated by nuclear bombs.

Our one window of opportunity to prevent this will occur within the term of whoever becomes President of the United States next January.

At a time like this, we do not have the luxury of waiting for our ideal candidate or of indulging our emotions by voting for some third party candidate to show our displeasure— at the cost of putting someone in the White House who is not up to the job.

Senator John McCain has been criticized in this column many times. But, when all is said and done, Senator McCain has not spent decades aiding and abetting people who hate America.

On the contrary, he has paid a huge price for resisting our enemies, even when they held him prisoner and tortured him. The choice between him and Barack Obama should be a no-brainer.

To find out more about Thomas Sowell and read features by other Creators Syndicate columnists and cartoonists, visit the Creators Syndicate web page at www.creators.com. Thomas Sowell is a senior fellow at the Hoover Institution, Stanford University, Stanford, CA 94305. His Web site is www.tsowell.com.

COPYRIGHT 2008 CREATORS SYNDICATE, INC.