groundswell

1. (nautical, surfing) A broad undulation of the open ocean, often as the result of a distant disturbance.

2. (by extension) A broadly-based shifting of public opinion.Examples: "An astonishing groundswell of support for the new Democratic frontrunner, Barack Obama, is threatening to sweep Hillary Clinton away in New Hampshire, which holds the first primary election of the 2008 presidential contest tomorrow."; "The 1987 book British Piers was written at a time when Britain's seaside resorts were perhaps at their lowest ebb, with a groundswell of support for rejuvenation and conservation just beginning."; "The public’s endorsement of the war lacks the patriotic groundswell that greeted the annexation of Crimea in 2014."broadly