However, both two Democrats got higher points in handling the health care, the top concern for almost 20 percent of voters, almost twice as many as the 10 percent that cited terrorism.

The two Democratic presidential candidates are still caught in a close tie after most states and territories held their Democratic primaries and caucuses, with Obama's slight lead over Clinton in the number of delegates who would vote at the nomination convention in late August.

On Republican side, McCain would officially get the party's presidential nominee at the national convention in early September.

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raqi Prime Minister Nuri al-Maliki (R) meets US Republican presidential candidate John McCain (L) in Baghdad March 17, 2008. (Xinhua/Reuters Photo) 

(Xinhua News Agency March 19, 2008)