Next US president's diplomacy

In 1964, Senator Barry Goldwater proclaimed that his nomination as the Republican Party's candidate for president of the United States ensured that voters would be provided with "a choice and not an echo".

Now that it is clear that Barack Obama and John McCain will become the major nominees for the 2008 presidential election, analysts are seeking to determine where the two candidates stand on critical foreign policy issues.

Do they provide Americans with a genuine choice? Or do the two men differ only marginally?