Invoking the specter of Joe Biden and decrying Democrats whom he says have “clung to the status quo, insisted on using the same old playbook – and isn’t fighting hard enough,” Rep. Seth Moulton launched a primary challenge on Wednesday against Massachusetts Sen.

As Moulton laid out in an exclusive interview with the Globe, he wants the race to center on an incumbent who, in his view, is too old to represent a state that expects its senators to be national pla...