BOSTON — Former Kansas Gov. Kathleen Sebelius is planning to campaign on behalf of Democratic U.S. Senate hopeful Elizabeth Warren.

Warren’s campaign said Sebelius will join supporters for a canvassing kickoff in Porter Square in Cambridge on Saturday.

Campaign officials say Sebelius will be speaking on behalf of Warren’s as a private citizen and not in her official role as U.S. Health and Human Services Secretary for the Obama administration.

The campaign says Sebelius will talk about Warren’s efforts to create a level playing field for working families and small businesses.

Warren is challenging incumbent Republican U.S. Rep. Scott Brown in what is already the most expensive political contest in Massachusetts history.