The Democratic results Tuesday set up a clear two-person race between Obama and Clinton ahead of contests in Nevada, Michigan, and South Carolina, analysts say.
McCain's victory revives his campaign. But with limited money and stiff challenges in other states, it does little to clarify the race for the Republican nomination.
"I don't see that anyone has really demonstrated the knack to be called a frontrunner," says William Mayer, a political scientist at Northeastern University in Boston.
A record 500,000 people – about 62 percent of registered voters – were estimated to have turned out at the polls on an unseasonably warm January day. For voters in both parties, the economy and the war in Iraq were top issues, according to exit polls.
In the Democratic primary, the results, with 96 percent of precincts reporting, were 39 percent for Clinton; 36 percent for Obama; 17 percent for former North Carolina Sen. John Edwards; 5 percent for New Mexico Gov. Bill Richardson; and 1 percent for US Rep. Dennis Kucinich.
