Clinton has been battling to halt Obama's streak of eight wins, particularly if she hopes for any traction going into the bigger state contests in Texas and Ohio on March 4 that are key to her push to be the U.S.'s first female president. Obama is trying to become the country's first black president.
The 13-page blueprint for fixing the economy, released by her campaign on Monday, details the former first lady's plans to achieve universal health care, address the home foreclosure crisis and develop jobs for the middle class. These are core issues now for a majority of Americans amid fears of a recession, and are likely to resonate well in states like Wisconsin and Ohio with agricultural or industrial economies hit hard by job losses and the subprime mortgage and credit crunch.
Polls show a tight race in Wisconsin, even as Clinton's advisers have publicly downplayed their expectation for the state. Wisconsin offer the winner a hefty 92 delegates while Obama's native Hawaii, which holds its caucuses also on Tuesday, offers 20.
Although reporters normally travel everywhere with Obama, he left them behind Sunday to fly to North Carolina in secret from his hometown of Chicago to meet with Edwards. His campaign confirmed the meeting, but would not comment on the possibility of an endorsement.
Obama told Milwaukee television channel WITI-TV on Sunday the meeting was "was to "talk about how we can move the party in a direction that focuses on middle-class issues - relieving poverty, reducing the influence of special interests in Washington."
Edwards dropped out of the Democratic race after failing to win any of the earlier state races. Both Democratic candidates are actively seeking his support because of his appeal to working-class Democrats who are heavily represented in Ohio's primary and Pennsylvania's April 22 contest.
Obama, who usurped Clinton as the leader by a slender margin last week, was campaigning Monday in Wisconsin, where he has been for most of the week. Clinton arrived in Wisconsin on Saturday after spending most of the week campaigning in Ohio and Texas.
The former first lady had scaled back plans to campaign in Wisconsin, but will now try to squeeze in some stops on Monday that she was forced to cancel over the weekend because of a snowstorm.
Clinton's economic pamphlet, to be distributed to voters at campaign events and posted online, outlines many of the ideas she talks about on the campaign trail each day. But by pulling them together, the document resembles a populist manifesto - with Clinton championing the needs of working-class voters over corporate and business interests.
"Over the past seven years, big corporations and special interests have been given a free pass to profit, often at the expense of the American worker. As President, Hillary will make it a priority to scale back special benefits and subsidies to these corporations and put those resources to work for our economy again," the pamphlet declares.
After winning eight straight head-to-head contests, Obama led the chase for nomination delegates 1,280-1,218. It takes 2,025 delegates to secure the presidential nomination at the party's convention this summer in Denver.
In the Republican race, McCain, a former prisoner-of-war, has struggled to win over conservatives who view him as a political maverick out of step with the party on key issues like tax cuts, immigration and campaign finance reform.
McCain also competes in Wisconsin, with 40 delegates at stake, but the race is essentially over as he has 903 delegates to preacher-turned-politician Mike Huckabee's 245. A total of 1,191 delegates are needed to secure the party's nomination, and Huckabee has refused to drop out of the race until the veteran Arizona senator reaches that number.
The endorsement by the elder Bush, the patriarch of the Bush family, comes on the heels of former rival Mitt Romney's endorsement last week.
The former president is viewed as a moderate, and his endorsement may not directly help McCain win over conservatives. But it sends a clear message to all Republicans that they must back McCain if the party hopes to successfully confront either Obama or Clinton in the Nov. 4 general election.
Bush's endorsement was expected Monday, Republican officials said, speaking on condition of anonymity to not pre-empt the announcement.
With no such clarity emerging in the Democratic race, Clinton and Obama continued to trade barbs and look for ways to undercut each others' credibility. Clinton's advisers argued Sunday that Obama had abandoned a commitment to accept public funding if he wins the Democratic presidential nomination.
Last week, Obama's campaign walked back from a proposal the Illinois senator made last year to accept public financing for the general election if the Republican nominee also agreed to do so. Such a commitment would level the financial playing field with McCain, whose campaign has had a harder time raising money than Obama, who has broken all fundraising records.
Candidates who take public funds for the general election would have to return the money they raised.
Obama's campaign said accepting public financing was an option he would consider if he wins the nomination, rather than a hard pledge.
Clinton advisers seized on the shift, suggesting it highlighted Obama's pattern of making promises to voters and revising them later as circumstances change.
Obama's campaign fired back, with Obama spokesman Bill Burton saying Clinton was in no position to criticize since she had accepted more "money from lobbyists than any other Republican or Democratic candidate who's run for president.
Clinton next heads to Ohio, where her husband, former President Bill Clinton, was already campaigning Sunday.