Nearly half of Republican women voting in the primary said they couldn't imagine supporting him.
"We are seeking solid Democrats to run against them in the primary," said Kevin Finnegan, the union's political director.
"Simon has gotten no traction from his upset in the primary," said Sherry Bebitch Jeffe, a political scientist at the University of Southern California.
The Detroit News, which otherwise enthusiastically endorsed Mr. Romney in the primary, said he was dead wrong about the bailout.
"Bush has been here twice since the primary," said Ms. Napolitano, who has tracked the moves by the Republican opposition since the state's Democratic primary in February.
But Michael Lighty, the director of public policy at National Nurses United, a group that endorsed Sanders in the primary, said the senator's speech "could get contentious".
"Active Republicans are concerned that this will make it harder to bring the various groups together after the primary," said Mark Parkinson, the Kansas Republican chairman.
(Four years ago, Mr. McCain, before winning the primary, said on the campaign trail that climate change was a real, man-made problem that needed to be addressed).
Josh Isay, campaign manager for Andrew M. Cuomo, the former federal housing secretary and a candidate in the primary, said, "We are favorably inclined" to participate.
"One young man got a red flag from the White House because they found out he had donated $250 to McCain in the primary," said Mr. Weaver.
