In what is now a rite of passage, several presidential candidates are cleaning, mopping floors and performing other low-level job tasks to establish their credibility with the labor crowd.

Sen. Barack Obama (D-IL) is the most recent candidate to participate in the Service Employees International Union’s “Walk a Day in My Shoes” program. He spent two hours cleaning, folding laundry and preparing breakfast with a home healthcare worker. The program is a pre-requisite for endorsement consideration by the SEIU, which has 1.9 million members.

Sen. John Edwards (D-NC) also recently participated in the program, working a morning shift as a nurse’s aide at a nursing home. Other Democratic presidential candidates who have been in the program are Sen. Chris Dodd (D-CT) and Gov. Bill Richardson (D-NM).