Romney won a home state victory in Massachusetts. He also took Utah, where fellow Mormons supported his candidacy. His superior organization produced caucus victories in North Dakota, Montana, Minnesota and Colorado, and he, too, breathed defiance. "We're going to go all the way to the convention. We're going to win this thing," he told supporters in Boston.
Democrats played out a historic struggle between two senators: Clinton, seeking to become the first female president, and Obama, hoping to become the first black to win the White House.
Clinton won at home in New York as well as in California, Massachusetts, New Jersey, Oklahoma, Tennessee, Arizona and Arkansas, where she was first lady for more than a decade. She also won the caucuses in American Samoa.
Obama won Connecticut, Georgia, Alabama, Delaware, Utah and his home state of Illinois. He prevailed in caucuses in North Dakota, Minnesota, Kansas, Idaho, Alaska and Colorado.
After an early series of low-delegate, single-state contests, Super Tuesday was anything but small -- its primaries and caucuses were spread across nearly half the country in the most wide-open presidential campaign in memory.
The result was a double-barreled set of races, Obama and Clinton fighting for delegates as well as bragging rights in individual states, the Republicans doing the same.
The allocation of delegates lagged the vote count by hours. That was particularly true for the Democrats, who divided theirs roughly in proportion to the popular vote.
Nine of the Republican contests were winner take all, and that was where McCain piled up his lead.
The Arizona senator had 522 delegates, to 223 for Romney and 142 for Huckabee. It takes 1,191 to clinch the presidential nomination at next summer's convention in St. Paul, Minn.
Overall, Clinton had 706 delegates to 611 for Obama, out of the 2,025 needed to secure victory at the party convention in Denver. Clinton's advantage is partly due to her lead among so-called superdelegates, members of Congress and other party leaders who are not selected in primaries and caucuses -- and who are also free to change their minds.