Hillary Clinton gestures while standing beside Bernie Sanders during the first Democratic presidential debate | Getty Clinton memo touts union ties as Sanders allies grumble

Hillary Clinton's campaign will send its backers a memo on Wednesday outlining the Democratic front-runner's wide-ranging support from the labor movement — just one day after Bernie Sanders' campaign appeared to grumble that he is the true candidate supported from the rank-and-file — according to a copy of the note obtained by POLITICO.

The former secretary of state secured the backing from the Service Employees International Union on Tuesday morning, giving it the support of groups representing more than 10 million union members, by the campaign's count. The two-page memo, signed by Political Director Amanda Renteria and Labor Outreach Director Nikki Budzinski, touts that figure and reminds supporters of the candidate's 94 percent rating with the AFL-CIO.


It lands amid escalating tension between Sanders — whose supporters view him as the labor movement's natural ally — and Clinton.

"These endorsements are a critical addition to the campaign's efforts to mobilize, energize, and turn out voters, first in the early primary states and then throughout the primary calendar," the Clinton aides write, noting that 13 unions, including the 2 million member SEIU, 1.6 million member American Federation of Teachers, 1.6 million member American Federation of State, County and Municipal Employees, and 3 million member National Education Association, have backed Clinton.

"It's a critical advantage that expands the depth, breadth, and scope of the Clinton campaign's significant outreach, grassroots and field presence."

The campaign's document points to a litany of policy plans that are central to her labor pitch, including raising incomes and federal investment in infrastructure, increasing the minimum wage, and working for equal pay and collective bargaining rights, among others.

But the memo — and its pointed focus on the primary election — is unlikely to assuage griping from allies of Clinton's rival that she does not best represent unions' interests, and their contention that the groups' leadership teams are backing her despite Sanders' support from on-the-ground union members. Sanders and Martin O'Malley both support the SEIU's push for a $15 minimum wage, for example, while Clinton has expressed her own sympathy but only committed to supporting a $12 minimum wage nationally.

"We are gratified that hundreds of thousands of workers are part of the growing grassroots movement supporting Bernie's campaign to help working families by raising the minimum wage, providing health care for all and making college affordable," said Sanders' communications director Michael Briggs in a statement about rank-and-file SEIU members' backing of Sanders shortly after Clinton won the group's endorsement.

Sanders, for his part, has won some union support, including from the National Nurses United group. But the barbs between him and the front-runner has been ratcheting up in recent days, and the Clinton camp's memo will serve as a public reminder of her political muscle from the labor world.