Senator Marco Rubio, opening a more aggressive phase of his campaign as he tries to reinvigorate his bid for the Republican nomination, suggested Thursday that Donald J. Trump may be too crude to be president and that Jeb Bush, the former Florida governor, may be too inexperienced.

Mr. Rubio expressed disgust with Mr. Trump’s use of obscene language earlier this week, describing how his two young sons had watched a news clip of Mr. Trump insulting Senator Ted Cruz on the eve of Tuesday’s New Hampshire primary. When the boys, age 8 and 10, asked their father what word had been bleeped out, Mr. Rubio said, he was at a loss.

“The commentator said it was another word for cat,” Mr. Rubio said in an interview on Thursday aboard his campaign plane, which touched down here for a rally. “My boys wanted to know, ‘What was the word? What was the word?’ I said, ‘I can’t tell you.’ I had to make something up. And it bothered me.”