Several of Joe Biden’s allies say they could see the former vice president picking Sen. Elizabeth Warren (D-Mass.) as his running mate to help unify the centrist and progressive wings of the party.

The speculation comes after Biden pledged to pick a woman as his running mate during the Democratic primary debate on Sunday.

Picking Warren would have its drawbacks, however, putting two septuagenarians at the top of the ticket from safe blue states.

“I think she represents a sort of bridge between the moderate land and progressive lane,” said one longtime Biden ally who is in touch with the campaign.