Political parties spend months interviewing potential candidates and scrutinizing their pasts, but their efforts don't always pay off.
Less than a week into the federal election campaign, candidates from the Liberal, Conservative, New Democrat and Green parties have already either stepped down or been disqualified by their parties.
Vetters say the screening process isn't broken, but it's far from foolproof.
Political parties' vetting strategies vary, but many rely on lengthy application forms, interviews and research teams.
The vetting process can take months, according to former United Conservative Party executive director Janice Harrington, who supervised candidate vetting during Alberta's recent provincial election.
Vetters go far beyond background checks and Google. They examine financial data and search for potential conflicts of interest. Some ask for social media passwords so they can comb through years of posts and comments.
"It is a lot more complicated than you think it is," Harrington said.
Who gets the green light?
Parties must weigh the risks and rewards if they discover compromising material associated with a valuable candidate, said Jack Siegel, a Toronto lawyer who led the Liberal Party's vetting committee during the 2015 federal election. Though Siegel isn't leading the party's committee this year, he is still involved with the Liberal campaign.
Vetters use their political judgment to decide whether or not to exclude a potential candidate. In some parties, like the UCP, the party leader gets the final say. Other parties, like the Alberta Party, ask a board of directors to vote on complicated cases.
Excluding a candidate is relatively rare, though, vetters told CBC News.
"I would be surprised if we excluded more than two or three per cent of the applicants in the 2015 election," Siegel said.
More often, parties use their research to anticipate and prepare responses for potential problems. This not only protects the party, said Conrad Guay, president of the Alberta Party's board of directors, but the candidate as well.
'You're not going to catch everything'
Some political parties hire companies to search applicants' social media history, but often that task falls to campaign workers and volunteers, who may catch some but not all problematic posts.
Last year, Alberta Party by-election candidate Sid Fayad apologized after a Facebook comment in which he used the N-word resurfaced.
Vetters missed the five-year-old comment during the screening process.
"It wasn't even something that we could have found, really," Guay said.
"Nobody's perfect and you're not going to catch everything."
Risks and rewards
Despite the high stakes and the substantial time commitment, vetters say their job is an important one that helps determine the quality of their parties' candidates.
Though Calgary political scientist Lori Williams argued there were problems with the UCP's screening process during the Alberta election, Harrington said she was happy with the quality of candidates who went forward.
Securing qualified candidates is the rewarding part of vetting, she said.
For Siegel, the big reward is winning.
"If you're part of that team, and particularly in my case, in 2015, when that team wins a majority government, it's really a rewarding feeling," he said.