Senator Barack Obama of Illinois and John Edwards, the former senator from North Carolina who was the party's candidate for vice-president in 2004, will participate in a call organised by the Wake Up Wal-Mart campaign aimed at mobilising protests against the retailer in the holiday shopping period.
Wake Up Wal-Mart is funded by the United Food and Commercial Workers, the grocery workers' union pursuing a broad political campaign against the retailer after a series of failed efforts to organise its workers.
Mr Edwards, regarded as an ally by the US union movement, was one of a number of top Democrats who participated in rallies organised by the Wake Up Wal-Mart campaign during campaigning for last month's elections. Mr Obama had not previously been actively involved in the anti-Wal-Mart campaign.
A spokesman for Mr Obama said he was participating "because he believes all workers in America, no matter who they work for, deserve to be paid a living wage and have access to comprehensive healthcare their families can afford."
Wal-Mart is expected to face increased pressure from the new Democrat-controlled Congress on a range of issues, from its application for a banking licence to healthcare provision and wages.
Lee Scott, chief executive, said during a discussion of the retailer's financial results yesterday that the company was "bipartisan", and cited its recent move to introduce low-cost generic drugs as an issue that reflected its shared interests with both parties.
"We believe that through an ongoing outreach programme we will be able to work with both parties, and continue to play the role which we play," he said, citing Wal-Mart's role in job creation and its recent environmental initiatives.
He also pointed to its role in "community building".
Wal-Mart has significantly increased political spending over the past four years, making contributions of $2.6bn (€2bn, £1.4bn) in the run-up to this month's elections, against $1.4m for the mid-terms four years ago.
Roughly two-thirds of the money went to Republican candidates. Its largest individual contributions of $10,000 went to five Republicans in the fiercely contested Senate races in Virginia, Ohio, Minnesota, Missouri and Arizona, with only one – Senator Jon Kyl of Arizona – emerging victorious.
Wal-Mart also demonstrated a new readiness to engage with campaign debates, using its new support group, Working Families for Wal-Mart, to respond aggressively to criticisms from Democratic candidates of its healthcare and wages.
