Groundswell

a buildup of opinion or feeling in a large section of the population

a sudden increase in people's feelings about something

a sudden gathering of force, as of public opinion: a groundswell of antiwar sentiment.

a growth of strong feeling among a large group of people

(Physical Geography) a considerable swell of the sea, often caused by a distant storm or earthquake or by the passage of waves into shallow water

a strong public feeling or opinion that is detectable even though not openly expressed: a groundswell of discontent.

A sudden gathering of force, as of public opinion: a groundswell of antiwar sentiment.

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There is a groundswell of opinion against the new rules.

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To convey these values, the Obama campaign claims to be taking grass-roots organizing to a new level, harnessing what they describe as a groundswell of enthusiasm.

Ex.

A sudden gathering of force, as of public opinion: a groundswell of antiwar sentiment.

Ex.

A broad deep undulation of the ocean, often caused by a distant storm or an earthquake.