The fierce battles for the U.S. presidential nominees were expected to escalate during a two-week break from Wednesday to March 4 when Ohio and Texas hold their primaries and caucuses.
Illinois Senator Barack Obama, who is currently slightly leading the Democratic presidential race, was seen to become the bull's eye attacked by his strong rival, New York Senator Hillary Rodham Clinton, and Republican sole forerunner John McCain.
The African American candidate prevailed in two more primaries in Washington and Wisconsin, and was expected to win the caucuses in his birthplace of Hawaii that ended around 13:00 EST on Wednesday (0600 GMT).
He has added to 1,301 the number of the delegates who would vote for him at the party's presidential nominee convention late August, leading Clinton by 62.
Moreover, seen from Wisconsin, Virginia and Maryland primaries, Obama has significantly cut into Clinton's supporter base whose main components are women, low-income and blue-collar voters.
Before, the votes he gained mainly came from young, black, more wealthy and educated groups.
However, Obama's lead can not be sustained if he fails to diminish in the next two weeks Clinton's prevalence in the populous states of Ohio and Taxes, which would yield 141 and 193 Democratic delegates respectively.
Earlier polls showed the two states both set up well for the former First Lady, with a number of workers hit by industrial recession in Ohio and a large Latinos community in Texas.
Driven by a strategy to at least keep a close split in the delegates with Clinton on March 4, Obama's campaign is expected to focus on his newly-released economic plan in the November national elections against McCain.
The two Democrats would be also intensifying their fight for a total of 800 "Super delegates" who are awarded to the party's senior members and officials.