Hand-sitter

A key factor in Nelson Rockefeller's noncandidacy decision was the failure of the Republican governors—and leading liberal Republicans—to come out for him publicly after New Hampshire. There were personal telephone calls urging him to run, but that was all … Among the biggest hand-sitters was a former Republican governor […]

Source: wiktionary

They were such a responsive audience, for one thing, so unlike the academic hand-sitters he was used to, and they'd turned out in such large numbers, despite a heavy downpour, filling the basement of the First Presbyterian Church to capacity, even standing in the back and along the walls.

Source: wiktionary