Jackson quickly came forward to replace Platner, and his organizing muscle turned what was shaping up as a contentious process to pick a new candidate into a foregone conclusion.

Over the weekend, when county parties met to select delegates to Saturday’s statewide convention, they voted in overwhelming numbers for delegates who had pledged their support for Jackson.

But even if the convention is now shaping up as a coronation, Jackson’s path ahead is fraught.

Many Maine Democrats are still mourning the collapse of Platner’s campaign and hoped for someone to continue his message.

The populist Jackson will need to unite Democrat factions — something he failed to do in the gubernatorial primary.

He must also contend with fresh scrutiny of his past social conservative positions, his alliance with Platner and defenses of him as scandals mounted, and his conduct as state Senate president, which came under fire Monday amid reporting about his allegedly volatile temper.

Jackson has no time to get his bearings, with his inevitably brutal, expensive, and hard-fought contest against Republican Senator Susan Collins just over 100 days away.

“She’s had years to stand up for working people, and she hasn’t done a damn thing,” Jackson said in a statement released Monday morning.

“I’m running because Maine deserves someone who’s going to deliver for them and fight like hell for the people who work for a living.” Maine voters will hear that pitch often until November, but it’s also the same basic pitch Jackson has been consistently delivering throughout a decades-long political career defined by his staunch advocacy for organized labor.

“Troy is a very old-fashioned Democrat,” said Anthony Emerson, a Portland native who ran as a pro-Jackson delegate to the convention.

“He is a labor guy through and through.” Sarah Nichols, the former mayor of Bangor and a close Jackson ally, says she has a running joke with friends.

“If there’s a picket in Maine,” she said, “Troy is there, whether or not you called him.” Jackson will advance the same style of politics that propelled Platner from obscurity to political sensation.

Many Democrats hope that he can recapture the energy behind Platner and harness it to defeat Collins.

But his closeness to Platner -- the two campaigned together frequently -- will immediately open Jackson up to Republican attacks.

The Republican National Committee dubbed Jackson “Graham Platner 2.0” and knocked him for defending Platner amid his many previous controversies.

They also hit him over backing the same progressive policies as Platner, including enacting Medicare For All and abolishing the Immigration and Customs Enforcement agency.

On Monday, The Washington Post reported on a pattern of Jackson losing his temper with colleagues as Senate president, particularly women.

In one episode, Jackson allegedly threw a water bottle toward another Democratic senator during a heated meeting before “haranguing” her extremely close to her face.

(Through a spokesman, Jackson acknowledged moments of anger but denied throwing anything at anyone.) In theory, supporters have believed Jackson is suited to champion a left-wing populist platform, given his hard-won labor bona fides and humble roots.

There is a recurring quip in state Democratic circles that Jackson genuinely is who many people believed Platner was.

At the same time, where Platner was a talented speaker perfectly suited to today’s viral clip-driven world of political media, Jackson is a halting speaker, low-key and some would say unpolished.

He speaks in an accent not often found outside parts of northern Maine and Canada.

“He comes....