Mr. Bush has always taken a path separate from those of his brother and his father, and friends said his words were those of a man free from the restraints of electoral politics. He said on CBS last week that he had no interest in being vice president to Mitt Romney — whom he has endorsed — and that while he has not ruled out a presidential run in the future, this year was “probably my time.”

But his comments gave voice to the growing drift of the party’s base from the Bush family, which has become all the more acute as this year’s Republican presidential contenders, including Mr. Romney, appeared to wipe his brother George’s eight years in the White House from their collective memory bank.

When President George W. Bush’s tenure was mentioned at all during the nominating fight, it was frequently done in a negative light, as the candidates criticized his expansion of the Medicare prescription drug benefit, the Wall Street bailout and his signature education initiative, No Child Left Behind.

But friends say it is the party’s shift away from the sort of comprehensive immigration overhaul Mr. Bush had championed during his presidency that particularly pains the Bushes, who, for all of their differences, believe the system should be more humane for hardworking and law-abiding Hispanic families — whom the Republican Party must court to assure its future success. The issue has particular resonance for Jeb Bush, whose wife, Columba, is of Mexican heritage.

“It is a Bush family belief that we have to do more with Hispanic voters,” said a friend of Jeb Bush, Ana Navarro. “But Jeb understands the Republican Hispanic dynamic better than most people do because he speaks the language, he reads and listens to the news coverage, and he lives in the community.”