McCain is now piling up delegates. ABC News estimates McCain has secured 561 delegates to date to 222 for Romney. Huckabee stands at 172. To win the GOP nomination 1,191 delegates are needed.
Huckabee has also done better than expected, winning a surprise victory in West Virginia, winning Alabama, Tennessee Georgia, and his home state of Arkansas, based on exit poll analysis. Romney won victories in Colorado, Utah, Minnesota, North Dakota, Montana and Massachusetts, according to exit poll analysis.
While McCain stands to cement his front runner staus in coming primaries, the Democratic delegate picture remains cloudy. On Saturday, Louisiana and Washington state hold two-party contests while Nebraska Democrats and Kansas Republicans make their picks. Then comes a larger series of two-party primaries in Maryland, Virginia and the District of Columbia on Tuesday.
In an encouraging sign for her candidacy, Clinton won Massachusetts even though Obama received endorsements from Massachusetts Sens. Ted Kennedy and John Kerry.
Exit poll results suggested Clinton owes her victory in the Bay State to a large turnout by women and a sizable gender gap -- with more women supporting Clinton and more men supporting Obama. Her victory in New Jersey is also being credited to a high turnout of women who supported her, according to exit poll analysis.
In his home state of Illinois, exit polls indicated that Obama claimed the majority of votes cast by white women, Clinton's core group in most states. In Georgia, 88 percent of the record turnout of black voters backed Obama, according to preliminary exit poll results, mirroring Obama's success among black voters in South Carolina.
The Democratic race is a heated contest between Clinton, whose once commanding lead in key states diminished as Super Tuesday approached, and Obama, the charismatic senator who had mega-star supporters like Oprah Winfrey, Caroline Kennedy and California first lady Maria Shriver stumping for him this weekend.
Preliminary exit poll results suggest Obama's message of "change" resonated with Democratic voters today; they were twice as likely to say they are interested in the candidate who can best "bring needed" change over the candidate with the best experience and other attributes.
Hispanics and women -- two key demographics targeted by Clinton -- turned out in high numbers, according to preliminary exit poll results.
But with the way results were shaping up, those looking for a clear front-runner to emerge in the Democratic race could be waiting for months.
"They're in a real dogfight," California-based Democratic strategist Bill Carrick told ABC News. "It's really going to be about who can grind it out, who can raise money and stay in the game the longest."
Both campaigns were managing expectations Tuesday, with Plouffe defining victory for Obama as being "close" to Clinton in pledged delegates by the end of the night, reports ABC News' David Wright and Sunlen Miller.
Meanwhile, Clinton's chief strategist Mark Penn told reporters even if Obama finishes the day having won more delegates, they are confident Clinton will maintain an overall delegate lead including superdelegates.
Both the Clinton and Obama campaigns have vowed to fight all the way to the convention.