Del Mastro and his former official agent, Richard McCarthy, are charged with filing a 2008 campaign return that was false or misleading, exceeding the legal election spending limit, and filing a return that omitted required information.
Del Mastro is also charged with exceeding the political contribution limit of $1,000 by writing a $21,000 personal cheque that allegedly went into his own campaign.
A conviction could mean fines of between $2,000 and $5,000, a sentence of up to five years in prison, or both.
But just last week, Del Mastro, who served as Harper’s parliamentary secretary, was shifted to the economic development portfolio. Parliamentary secretaries get $16,000 wage hikes on top of their MP salaries of $160,000 but are not members of cabinet.
"Historically, because the patronage system was very strong in the early days of Canadian parliamentary democracy … it made sense to have a system by which you could reward particularly loyal people," Abray-Nyman told Jordan Press. "This provided you with an additional layer to reward people."
Fans of question period know Del Mastro proved his loyalty as a frequent speaker, at least before this scandal began to take off, who would rise to defend the Harper government from allegations and fire back at members of the opposition.
But even outside the House of Commons, Del Mastro would toe the party line and mix it up with rivals.
Here are just a few of Del Mastro's memorable moments before he became, evidently, persona non grata to Conservatives.
'Why Mr. Speaker? Why?'
In June, Del Mastro broke down in the House of Commons while addressing the allegations concerning his 2008 campaign expenses.
The then-parliamentary secretary to the prime minister said he felt "violated" and betrayed by Elections Canada.
"I feel strongly that this process has been conducted with malice and contempt for me as a member and for my family's well-being."
High Praise For Harper
In an interview with the CBC's Evan Solomon this spring, Del Mastro was asked about the Wright-Duffy affair that was dominating headlines at the time.
He didn't hesitate to defend his boss.
"We have in Stephen Harper the most ethical prime minister that I believe this country has ever had," he said.
Stop Me If You've Heard This One..
Del Mastro got more than a little repetitive in March, 2012, while defending the government over the robocalls scandal.
'I'd Like To Thank The Member For 8 Mile..'
Del Mastro poked fun during question period in 2012 at MP Charlie Angus' rap number at the NDP Leadership Convention.
If you haven't seen Angus' rap, well, you simply must.
'Your Son Is A Member of Parliament'
Del Mastro gave a speech at the 2007 March for Life rally on Parliament Hill, where he thanked his mother for not having an abortion after becoming pregnant at a difficult time.
"The laws will change in this country, I believe that, God bless you all."
'Go To Their Average Adult Video Store..'
Last year, Del Mastro said a controversial sex education exhibit displayed at the Science and Technology museum in Ottawa wasn't science or biology.
"It's called biology Dean,” said Liberal MP and medical doctor Carolyn Bennett on CBC's "Power and Politics."
“No,” insisted Del Mastro. “It's not called biology, it’s called many things but it is not biology Dr. Bennett."
Del Mastro added: "People can go to their average adult video store if they want to see this type of thing."
In 2011, Del Mastro made headlines after he publicly questioned Liberal MP Justin Trudeau's adherence to the Catholic faith.
Del Mastro said on Facebook it was "outrageous" the Peterborough Catholic school invited Trudeau to speak to students.
"Are there any tenets of the Catholic faith that Justin supports?" he wrote.
Trudeau said at the time he was "surprisingly upset" at the insult.
"For someone to start questioning my own faith and accusing me of being a bad Catholic, is something that I really take issue with. My own personal faith is an extremely important part of who I am and the values that I try to lead with."
Last October, Del Mastro used his member's statement to suggest Parliament should move to regulate anonymous commentary online.
"Yesterday I read the comments of hundreds of anonymous posters online and was frankly shocked and saddened by the level of vitriolic hatred and personal attacks that were freely posted," he said. "While I believe firmly that the right to free speech must be strongly defended and protected, I also believe it should be backed up by the common decency to stand by one's words as opposed to hiding behind online anonymity."
Many Canadians took to Twitter to poke fun at Del Mastro and suggest he had just discovered the Internet. The hashtag, #DelMastroInternet, soon began trending.