But Mrs. Clinton has not picked on Mr. Bush at random: Her aides, for the most part, believe he is likely to ultimately win the Republican nomination. And in a very crowded Republican field, in which Donald J. Trump is sopping up the news media’s attention, Mr. Bush has for the most part escaped the kind of sharp elbows that would normally have been thrown at such a high-profile candidate.

Mrs. Clinton seems happy to pick up the slack. She faulted his record on voting rights. She ridiculed him for saying that Americans need to “work longer hours.” And she went out of her way, in a CNN interview, to point out that Mr. Bush no longer supported a path to citizenship for undocumented immigrants…

“This is the strategy of a weak Democratic candidate: to attack and be attacked by Jeb Bush, to rally Democratic antibodies to her defense and get her through an uncertain nomination process,” said Alex Castellanos, a Republican strategist…

“It should help him that Hillary’s attacking him,” said Joe Trippi, a Democratic strategist. “Unfortunately, the weird way the G.O.P. is situated right now, it probably won’t.”