Democratic White House hopeful Barack Obama has cast his ballot in his home city of Chicago with his young daughter Malia by his side.

In a historic vote that could make him the first black US president, the Hawaii-born Illinois Senator, joined by his wife Michelle Obama and his young daughters Sasha and Malia, was greeted at a Chicago polling station in a school gymnasium by dozens of reporters and photographers.

Obama, who is leading Republican John McCain in national polls, showed his daughter his ballot and smiled as he cast his vote.