The Democratic battle is dominated by a row over comments made by Barack Obama's former pastor, the Rev Jeremiah Wright, and a speech given by Mr Obama tackling the issue of race head-on. The Republicans' presumptive nominee John McCain visits Iraq, the Middle East and Europe. The US state department reveals that the passport files of Mr Obama, Hillary Clinton and Mr McCain have been improperly accessed.

"I can no more disown him than I can disown the black community. I can no more disown him than I can my white grandmother."
Barack Obama explains why he cannot cut off his former pastor in a landmark speech on race in Philadelphia

Visiting Iraq... it just becomes so palpably clear what a mistake it would be if the United States precipitously withdrew our forces John McCain At-a-glance: 8-14 March

"Your candidacy is a once-in-a-lifetime opportunity for our nation and you are a once-in-a-lifetime leader."
New Mexico Governor Bill Richardson endorsing Mr Obama as his choice to be Democratic nominee

"I do not see how two of our largest and most significant states can be disenfranchised and left out of the process of picking our nominee without raising serious questions about the legitimacy of that nominee."
Hillary Clinton, arguing that Michigan and Florida should not lose their delegates to the Democratic national convention

"Visiting Iraq... it just becomes so palpably clear what a mistake it would be if the United States precipitously withdrew our forces."
Arizona Senator John McCain on his first visit to Iraq since effectively sewing up the Republican nomination

"The Democrats have to ask themselves a question today. Do they really want the presidential campaign to be about race, because Barack Obama has made it now about race."
Rush Limbaugh, conservative talk show host, responding to Mr Obama's speech on Tuesday

A CBS News poll finds that 69% of voters who have heard or read about Mr Obama's speech on race say he did a good job addressing the issue of race relations, and 63% of voters say they agree with his views on the subject.

Seven out of 10 of those surveyed say Mr Obama did a good job of explaining his relationship with Rev Wright.

Overall, 70% of those surveyed say the row over Rev Wright's comments and Mr Obama's speech has made no difference to whether they would vote for Mr Obama; 14% say it would make them more likely to vote for Mr Obama, 14% say less likely.

However, the percentage of registered voters who believe Mr Obama would unite the country if elected falls to 52%, from 67% last month.

Barack Obama's speech sought to dampen down a row over his former pastor's "incendiary" comments and tackle the issue of race relations