Dimitri Soudas held privileged positions in the Conservative Party, including as one of Prime Minister Stephen Harper's closest allies.

He went on to become the party's executive director, after leaving the Prime Minister's Office to spend two years working for the Canadian Olympic Committee. He was fired last spring after interfering in the Oakville North-Burlington nomination race of his fiancée, MP Eve Adams.

Adams announced Monday that she is crossing the floor from the Conservatives to join the Liberal Party and plans to seek the Liberal nomination in Eglinton-Lawrence, the Toronto riding currently held by Finance Minister Joe Oliver.

Liberal officials insist Soudas won't do anything more than help put up Adams's lawn signs during the campaign. But every party has opposition researchers, masters of the political dark arts who keep an eye on what the other parties' MPs are up to, and Liberal Party researchers will be keen to talk to anyone who knows where the Conservative secrets are kept.

Soudas didn't respond to a text message requesting comment. His voicemail box was full and didn't allow CBC News to leave a phone message.

As Adams joins the Liberal Party, here are five ways Soudas could hurt the Tories by spilling to the Liberals.

1. Giving up campaign strategy

Soudas was brought in as the party's executive director specifically to plan for the 2015 election. While he was fired from that role more than a year before the Oct. 19, 2015, fixed election date, he would still have vast knowledge of what the Conservatives had in store for the Liberals and the NDP. He would also know, thanks to his time on the 2011 campaign (and the previous three campaigns), how the party allocates its spending.

"He will not just be pounding in lawn signs, I can guarantee you that," former Conservative cabinet minister Stockwell Day said Tuesday on CBC News Network's Power & Politics.

"Maybe Justin [Trudeau] himself will never talk to him so there's [plausible deniability] there, but he will be talking to people who are key strategists and who aren't afraid [of] pounding in other things."

2. Sharing debate tactics

Election debates are the only time during a campaign when the leaders face off and discuss policy together. The debates can take days of preparation as each leader seeks to stand out and attract new voters or sway anyone who is undecided.

Dimitri Soudas and Eve Adams appear in a promotional flyer distributed by Adams's camp last year in the riding of Oakville North-Burlington. (CBC) Day says Soudas would have been closely involved with the debate prep sessions in past campaigns.

"We all have weaknesses, we all have strengths, so he would have worked on those areas [with Harper]," Day said.

One area in which the Liberals would be sure to take an interest is how to rattle Harper or push his buttons during the live televised debates. Soudas may also be able to predict how Harper plans to try to throw Trudeau off his footing, or trap him verbally.

3. Giving away Harper's pressure points

Along with his knowledge of debate strategy, Soudas would know more generally how the prime minister thinks.

Day says Soudas was with Harper all day, every day when he worked for him — "probably like nobody else, because he was right with him in virtually every moment, especially related to communications and strategy."

"Think about that. You are going to see, over a period of weeks, months and years, some moments of frailty," Day said.

The same goes for the Conservative caucus: Soudas knows which ministers don't get along and which tactics would work best to drive a wedge between them.

4. Pointing to dirt on MPs and candidates

Soudas has a long history in the party and was often the one who fixed problems for Harper. He'd know which MPs have colourful elements in their pasts that they don't want revealed

"He knows what it is to play very tough hardball, as they say, to put on the brass knuckles," Day said.

"He knows what it is to be in the back alleys. So as much as he used to be very loyal, those loyalties obviously seem to have shifted."

5. Resurrecting past scandals

Liberal researchers will also want to ask Soudas about upcoming political landmines and dormant scandals.

For example, questions surfaced in 2011 about Toronto's Eglinton-Lawrence riding because of the number of special ballots used, the fact that many of the forms used to get them weren't properly filled out, and because former Liberal MP Joe Volpe complained of voters getting harassing and poll-moving phone calls.

That's the same riding in which Adams is seeking the Liberal nomination.

Day said Soudas was a friend of his for years, but that he sees a possibility the former director of communications for Harper will whisper secrets to the Liberal Party he so long fought against.

However, Day said, it's equally possible people will place less stock in what Soudas says, knowing the dramatic events that led to his firing.

Even so, "he's got a pile of information. There can be some collateral damage. I don't believe it'll be mortal," Day said.