Final answer:
The rhetorical device used in the passage from Margaret Chase Smith's 'Declaration of Conscience' is a simile, comparing the spread of suspicions to cancerous tentacles.
Step-by-step explanation:
The rhetorical device featured in the passage from "Declaration of Conscience" by Margaret Chase Smith is a simile. Smith compares the spreading of psychologically divisive suspicions and attitudes in the United States Senate to the spread of 'cancerous tentacles,' suggesting that these divisions and suspicions spread in a harmful and pervasive manner, similar to how cancer spreads through the body. This use of simile intensifies the detrimental effect that she believes such attitudes have on the society.