Hillary Clinton holds the Massachusetts Democratic institution.

Bernie Sanders has the progressive grassroots.

It's an odd balance that's mirrored in the latest polls, which show a solid tie. The race is rising up to be a test of institutional influence versus grassroots vigor.

Top leaders from Beacon Hill to Capitol Hill stood behind Clinton from the beginning, pitting them against a growing group of Sanders supporters, many of whom were activated four years ago by the message of another senator: Elizabeth Warren.