The industrious partner with the Toronto law firm Cassels Brock and Blackwell has been the legal bulwark of the Conservative party and some of its principal players since before the modern version of the party even existed.
So when Sen. Mike Duffy delivered his latest eye-popping revelations in the Senate expense drama this week, describing how his legal fees of more than $13,000 had been secretly paid by the Conservative party, the only unsurprising detail was that Hamilton handled the transaction.
Name a Harper government controversy that involved the Conservative party and you'll find Hamilton in the footnotes, if not in the executive summary.
From the "in-and-out" campaign funding charges in 2006 to the ongoing 2011 campaign robocalls investigation, the graduate of York University's Osgoode Hall is the party's chief legal firefighter.
The Toronto native and father of twins keeps a low public profile.
A search by the Library of Parliament turned up a few thin biographical sketches, belying Hamilton's linchpin role in some of the biggest political stories of the last decade.
"It's not my practice to participate in interviews like the one you're proposing," Hamilton amiably responded Tuesday when contacted by The Canadian Press.
"I'm the party's lawyer. I'm not the story. I'm here to assist those who are doing good work."
It was a response that may say more about the man than first glance: discreet, intelligent and with more than a hint of partisan flavour.
His online biography for Cassels Brock and Blackwell notes that he often handles employment issues, including "the detection and prosecution of employee misappropriation."
It also links to a January 2013 story in the Hill Times newspaper, which chronicles life on Parliament Hill, that named Hamilton the 11th most influential person in Ottawa. That put him right behind the powerful Clerk of the Privy Council, Wayne Wouters, and Nigel Wright, who was then Prime Minister Stephen Harper's chief of staff.
Wright, of course, has since left the PMO after being fingered last May for paying off Duffy's $90,000 in Senate expense claims.
The Conservative government's critics feel Hamilton has risen beyond the role of legal fixer and has entered the partisan fray.
Paying Duffy's legal fees for work done on the repayment of inappropriate expense claims should be construed as part of a coverup by the Prime Minister's Office and the Conservative party, said NDP Leader Tom Mulcair.
"Since the prime minister now claims that the whole deal was wrong, is he going to fire Arthur Hamilton?" Mulcair demanded in the Commons.
Liberal Marc Garneau also made it personal, stating in the Commons that, "Arthur Hamilton is well-known for mopping up ethical problems for the current government."
"Why did the prime minister's entourage pay Duffy's legal fees unless there was something very serious to cover up?"
Outside the House, where he has no immunity from being sued for libel, Garneau said, "We don't know what that ($13,560) cheque was for, precisely. It would be nice to know."
The suggestion that Hamilton did anything untoward does not sit well with his supporters.
"That's what lawyers do, they handle difficult situations," David Peterson, the former Liberal premier of Ontario, said from the Toronto offices of Cassels Brock and Blackwell, where he is the chairman.
Peterson called Hamilton "one of the smartest counsel in the country."
"He's got superb judgment. He's highly trusted. He's persuasive. He comes to the heart of the matter very, very quickly in understanding it.
"And if you're asking me if I'd rather he was a Liberal, I wish he was."
Hamilton has been involved with Conservative politics at least since his university days.
"Some people are afflicted for life," Peterson quipped. "I tried to convert him. I overlook him being a Conservative because of the core of his talents."
But partisanship is not the issue now for the Conservative party lawyer.
His decision to decline an interview for a newspaper profile speaks to where Hamilton would like to perform his professional services — in the background.
Garneau said the idea of the Conservative party lawyer becoming a household name in the capital is "not good."
"These guys, in the best of all worlds, never want their name to be known by anybody," said the Liberal MP and former astronaut.
"They supposedly should be like a shadow doing their job."
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