John Edwards and Rudy Giuliani drop out of election race

Clinton and Obama have also had harsh exchanges, but both toned down the rhetoric ahead of Tuesday's contests, in which 1,600 delegates are at stake. A total of 2,025 delegates are needed to secure the Democratic nomination at the party's convention in August.

Clinton was traveling Wednesday to Arkansas, where her husband, former President Bill Clinton, had been governor. She also planned to fly to Atlanta for a Democratic Party dinner.

Obama was heading for Denver and then Phoenix for campaign rallies in states with big Hispanic populations, an important constituency and one for which the two are competing hard.

AP photo