Mr. Bush’s rise in the polls, coming in tandem with Mr. Trump’s growing strength, may be a sign that so-called establishment Republicans are closing ranks around Mr. Bush, possibly as a result of Mr. Trump consolidating his own support. Marco Rubio may be feeling some of that shift with his sinking numbers.

The numbers suggest there may be very different approaches among the candidates to dealing with Mr. Trump, who has the media’s attention right now.

Mr. Bush’s rise in the polls suggests that his base of support has little overlap with Mr. Trump’s, and he therefore may have the least to lose in attacking the brash New Yorker. And Mr. Bush, in fact, has criticized Mr. Trump’s now-famous claim that many Mexican immigrants are criminals.

The rest of the field may take a more subtle approach to handling Mr. Trump. Attacking him head-on may risk alienating his supporters.