One of the most surprising things about the presidential election four years ago is that the already unpopular war in Iraq was not the top issue in voter's minds. Nor was it the top national security issue.

To get elected, Sen. John McCain needs something similar to happen this year. To construct such a scenario, it is helpful to reconstruct what happened four years ago.

By Election Day 2004, Americans were already unhappy with the war in Iraq. In the national exit poll conducted that day, 52 percent of voters said things were going badly in Iraq, while 44 percent said things were going well. Among the majority who thought the war was going badly, Sen. John Kerry defeated President Bush 82 percent to 17 percent.

Bush barely scraped out a victory despite the war. Why?

Obviously, when you are talking about an electorate that comprises millions of voters, there is no single answer. But the exit poll did point to some reasons, which can be analyzed within three great overarching issues: national security, the economy and the culture.

First, despite the dissatisfaction with the Iraq war, Bush still bested Kerry on the overarching issue of national security.

Even though 52 percent of voters thought things were going badly in Iraq, an even larger share -- 55 percent -- believed the war in Iraq was merely part of the larger war on terrorism. Eighty-one percent of these voters supported Bush.

Many voters decided that the broader war against terrorism -- i.e, al-Qaida -- was more important than Iraq itself. Thus, when voters were asked the most important issue in determining their vote, 15 percent said Iraq. Seventy-three percent of these supported Kerry. But an even larger share of the voters, 19 percent, said terrorism was most important. Eighty-six percent of these supported Bush.

In a similar vein, only 40 percent said they "trusted" Kerry to handle terrorism, while 58 percent said they "trusted" Bush.

A second factor that helped make the 2004 election close is that there were actually more voters (20 percent) who thought the economy-jobs was the most important issue than who thought terrorism was most important. Kerry beat Bush among these voters 80 percent to 18 percent.

This is surprising because gross domestic product grew by 3.6 percent in 2004, the highest annual rate of the Bush presidency. Nonetheless, according to the exit poll, 52 percent of voters in 2004 said they believed the national economy was "not good" or "poor."

Bush's trump card in 2004 was the third great issue: the culture.

More voters (22 percent) cited moral values as the most important issue in 2004 than cited either the economy (20 percent) or terrorism (19 percent). These voters supported Bush over Kerry by the same margin that economy-jobs voters supported Kerry over Bush: 80 percent to 18 percent.

According to 2004 exit poll, Sen. Barack Obama's "bitter" people -- those clinging to religion and guns -- voted for Bush by large margins. Continued...