What does it mean to 'move the needle'?

The expression “moving the needle” first appeared in England during the industrial revolution.  The reference was to gauges on steam engines.  During World War II, it became a more common term in reference to aviation gauges.  In business today it’s synonymous with making progress. Source

• In US politics to 'move the needle' is to significantly change the opinion polls in the direction of your candidate. 
• An alternative - more recent - origin to the one above comes from seismology. The movement of the Richter Scale indicates the strength of an earthquake.

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