Gerald Butts is the modern day Rainmaker, and the only one Trudeau trusts this election

Open this photo in gallery:

There are two powerful explanations for why Justin Trudeau brought Gerald Butts back as an adviser in the coming election campaign.

The first is that Mr. Butts is a modern-day Rainmaker, the nickname given to the late Keith Davey, who guided so many Liberal election campaigns from the 1960s through to the 1980s. The second is that Mr. Butts is one of the very few people the Prime Minister trusts.

“This is the smartest thing Justin has done,” enthused David Peterson, who was the Liberal premier of Ontario from 1985 to 1990. “Gerry is extraordinarily smart” and “Justin trusts him absolutely,” he said on Monday.

They say no one is indispensable. For Mr. Trudeau, Mr. Butts may be the exception. The Liberal Leader had to have him back, however great the risk.

And that risk is great. The Conservatives pounced on the news that Mr. Trudeau’s former principal secretary is back on the campaign team.

“The Lav-scam bully is in, and the principled women who spoke truth to power are out," Conservative MP Pierre Poilievre said at a news conference on Monday. "That’s everything you need to know about Justin Trudeau’s ethics.”

He was referring to Mr. Butts’s role in the SNC-Lavalin affair, in which Mr. Trudeau and his senior advisers urged Jody Wilson-Raybould, when she was attorney-general, to intercede in the criminal prosecution of the engineering firm. Ms. Wilson-Raybould eventually resigned from cabinet, joined in solidarity by fellow cabinet minister Jane Philpott.

Mr. Butts, then-principal secretary to Mr. Trudeau, resigned as well, in an effort to protect his boss. At the time, many of us thought he would never return, so close was he to the scandal, which had crippled the Liberal government. We were wrong. A senior adviser confirmed to The Globe and Mail’s Rachel Emmanuel that Mr. Butts will play an important, although undefined, role in the campaign.

Opinion: Butts is back. Now the question is whether he can renew Trudeau, too

Gerald Butts returning to take on important role in Liberal re-election campaign, party official says

Trudeau asks former chief of staff Cyrus Reporter, adviser Ben Chin to join him on Liberal campaign tour

Few things in this world are more difficult than managing a general election campaign. Different regions have different priorities. Polls and focus groups can only tell you so much. Managing the leader’s tour, and psyche, requires consummate skill. Only a handful of people in this country are up to the task. Mr. Butts is one of them. Without him, Dalton McGuinty’s Liberals might not have won the 2003 and 2007 Ontario elections. Without him, Mr. Trudeau might never have become Prime Minister.

Mr. Trudeau will also remember the lesson his father learned. After Pierre Trudeau became prime minister in 1968, he cast aside Mr. Davey and the other old hands who had steered the Liberal Party through the Diefenbaker and Pearson years. Mr. Trudeau paid for his arrogance by coming within two seats of losing the 1972 election. Immediately afterward, he got in touch with the Rainmaker, as Mr. Davey was called because of his ability to work political miracles.

Mr. Davey secured a majority government for Mr. Trudeau in 1974, and after the unpleasantness of the 1979 election – resulting in a short-lived minority Progressive Conservative government led by Joe Clark – engineered another majority for Mr. Trudeau in 1980.

Then there is the intangible element of trust. “First minister is a very lonely job,” Mr. Peterson observed, which is why so many politicians cling to a small group of advisers through good times and bad. Jean Chrétien had Jean Pelletier and Eddie Goldenberg; Paul Martin had David Herle, Terrie O’Leary and a couple of others. Even the notoriously solitary Stephen Harper had Ray Novak, and the late Doug Finley, who would be greatly missed in the 2015 campaign.

None of them were as close to their leader as Mr. Butts is to Justin Trudeau. The two have been best friends since university. Mr. Butts quit his job as head of the World Wildlife Fund Canada to manage Mr. Trudeau’s leadership campaign. He helped guide Mr. Trudeau to an unexpected victory in 2015. He sacrificed himself for his friend and leader by quitting as principal secretary.

The Liberals and Conservatives are running neck and neck in the polls. This election could go either way. So, of course Mr. Butts is back. There aren’t that many rainmakers around.

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.