Rathgeber leaves behind a growing group of colleagues frustrated with what is perceived as stifling control by Prime Minister Stephen Harper and his staff, and a drift away from the values of core Tory supporters.
At the same time, Harper has been pushed off his carefully crafted economic message by a Senate spending scandal that won't die. And an old rift over leadership voting that threatens to resurface at this month's party convention could add to the distractions.
Rathgeber, Conservatives say, was never regarded as a strong team player. Still, the Alberta MP said some of the same things other Tories grouse about in private, refusing to act as a mere "cheerleader" for the government.
"When you have a PMO that tightly scripts its backbenches, like this one attempts to do, MPs don't represent their constituents in Ottawa, they represent the government to their constituents," Rathgeber said in Edmonton.
Rathgeber's departure comes after several episodes of mostly polite rebellion by Conservative MPs:
— A dozen Tories, including Rathgeber, spoke out in the House of Commons about the autonomy of MPs and their right to make statements in Parliament without first clearing them with the party leadership.
— Several Conservatives said they would not mail out a taxpayer-financed pamphlet attacking Liberal Leader Justin Trudeau, which was produced by the Conservative research group.
— Saskatchewan MPs said they were caught flatfooted on the redistribution of ridings in their province because the party unwisely told them to back off early in the process.
— Caucus members are less than thrilled with how the Senate expenses scandal has been handled, and are watching flagging support in the polls with a wary eye.
Putting a fine point on Rathgeber's main gripe about control, colleague Brad Trost said Thursday he was disappointed in the way Harper's office responded to the resignation. Director of communications Andrew MacDougall tweeted Wednesday night that Rathgeber should resign his seat and run in a byelection.
"That was not a respectful way to handle this," said Trost.
Of several backbench MPs asked about Rathgeber on Thursday, not one would repeat the suggestion that he resign. Several said they liked the private member's bill that precipitated his resignation — one that was gutted by a group of Tory colleagues in a committee late Wednesday.
Opposition MPs delighted in the Tory turmoil.
"The true believers, the Prairie true believers, the Reformers, they were committed that they wanted to clean up Ottawa and things were going to be different," said outspoken New Democrat MP Pat Martin.
"No more patronage. No more scandals. Appointments to the Senate. All those things have been hard to swallow for those guys and they've dutifully sat there with their mouths shut and their lips zipped because of this iron fist of control."
But Ontario MP Daryl Kramp rejected Rathgeber's charge that the Prime Minister's Office exerts too much control over MPs and senators.
"You can still share the elements of where we need to go while having a difference of opinion," Kramp said.
"Sometimes there's strength in diversity of opinion, there's nothing wrong with that. But at some time you can't move in 307 different directions all at once."
Adding to Harper's difficulty is a similar vein of dissent inside the Conservative rank and file, which complains that party officials wield too much control at the expense of the grassroots.
These issues are expected to surface at the party convention in Calgary at the end of the month.
Defence Minister Peter MacKay warns that he, too, may be prepared to jump ship over fundamental questions about how the party elects its leaders in the future.
Throughout all this, there has been little direct criticism of Harper. Even Rathgeber has said he respects and supports Harper, but has a problem taking orders from the mostly young, unelected staff in the prime minister's office.
He pointedly noted that he took Harper at his word that he did not know about chief of staff Nigel Wright's controversial $90,000 cheque to Senator Mike Duffy to cover improper expenses.
"That sounds like an exoneration and it is to him," Rathgeber said.
"But I think it actually creates a much bigger problem and that is that the Prime Minister's Office seems to be accountable to nobody, not even the prime minister, that a decision of that magnitude could have been made and executed without even informing the prime minister."