How the 2015 federal election campaign unfolded:

August 2

Prime Minister Stephen Harper announces he has asked the Governor General to dissolve Parliament, triggering a campaign for the Oct. 19 election billed as one of the longest — and most costly — in modern Canadian political history.

August 6

Harper's economic and environmental records comes under fire during the televised Maclean's debate as NDP Leader Tom Mulcair, Liberal Leader Justin Trudeau and Green party Leader Elizabeth May took aim at the Conservative leader's nine-year tenure.

August 12

Harper's former chief of staff, Nigel Wright, begins his testimony at the criminal trial of Sen. Mike Duffy, telling court he informed Harper that Duffy agreed to repay his impugned expense claims, but did not disclose there was a plan afoot for the party to foot the bill.

August 17

With the Duffy courtroom drama playing out in Ottawa, Harper faces pointed questions about his current chief of staff, Ray Novak, after it emerged he was included on the email chain about Wright's plan to repay the senator's expenses.

August 22

Tory supporter Earl Cowan becomes angry with reporters on the Conservative campaign trail after they asked Harper about what was happening inside the Prime Minister's Office during the Mike Duffy affair.

August 27

Trudeau declares that a Liberal government would run deficits of up to $10-billion a year for three years until 2019 to help kick-start the economy.

August 28

An animated Harper uses a 'teeny-tiny' finger gesture to mock Trudeau's deficit plan.

September 1

Statistics Canada says the Canadian economy shrank for the second quarter of 2015, putting the country into its first technical recession in six years. The agency also reports Canada's GDP climbed in June by 0.5 per cent after shrinking over the first five months.

September 2

After campaigning with Paul Martin, Justin Trudeau says the former prime minister made the right decision when he slashed transfer payments to the provinces to balance the books. Trudeau, however, says he won't follow the same path.

September 3

After the photo of three-year-old Alan Kurdi — a dead boy found washed up on Turkish beach — circulates around the world, Harper says Canada needs to keep fighting Islamic militants, the root cause of the suffering in Syria and Iraq.

September 4

Harper continues to face calls on the campaign trail to speed up the processing of Syrian refugees.

September 14

Harper hits the campaign trail armed with good news: Finance Department released figures showing a $1.9-billion surplus for the 2014-2015 fiscal year.

September 16

On the eve of the economic debate in Calgary, the NDP releases a breakdown of its economic plans and promises to boost federal spending on health care beyond what Conservative budgets have forecast.

September 17

During the economic debate, Mulcair rips into the government's plan to ship Canadian crude to the U.S. Gulf Coast, arguing he wants to keep jobs in Canada instead of sending them south of the border.

September 19

Facing much scrutiny, the government says it will speed up the processing of Syrian refugee applications in an effort to issue "thousands more" visas before the end of this year.

September 23

During a speech in Montreal prior to the campaign's first French-language debate, Mulcair tries to blunt expected attacks from rivals over his opposition to the government's ban on face coverings at citizenship ceremonies.

September 28

Trudeau defends his father's political record during the Munk debate in Toronto, which is focused on foreign policy issues.

October 2

Conservative candidate and Immigration Minister Chris Alexander reminds Canadians about the “Zero Tolerance for Barbaric Cultural Practices Act,” and promises more government resources if Conservatives are re-elected, including an RCMP tip line.

October 6

Harper tells CBC News a Conservative government would consider banning public servants from wearing the niqab.

October 8

Harper says the Prime Minister’s Office temporarily halted the flow of Syrian refugees into Canada last June to verify that the most vulnerable people were being selected while ensuring security.

October 15

Trudeau defends the departure of Liberal campaign co-chair Dan Gagnier following a Canadian Press report that reveals he sent lobbying advice about the controversial Energy East pipeline to officials at TransCanada Corp.