Mr. Rubio’s heritage and his youth could be particularly dangerous to Mrs. Clinton, they said. Each of those points could help neutralize one of her biggest strengths: the opportunity to help elect the first female president, and the experience Mrs. Clinton gained as secretary of state.
Mr. Rubio already appears to be pursuing that strategy. By calling himself a candidate of the “21st century, not the 20th,” he seeks both to turn Mrs. Clinton’s long career against her and to entice voters who may desire a change of direction.
In Florida, Democrats who have watched Mr. Rubio’s rise warn against playing down his strengths.
Former Gov. Charlie Crist, who lost to Mr. Rubio in the Republican primary for the 2010 senatorial election but later switched parties, said he admired how Mr. Rubio told the story of his immigrant parents — his mother a maid, his father a bartender — and how they worked hard so that he could succeed. “It’s hard to get more compelling than that,” Mr. Crist said.
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