5 things to know about Graham Platner ally poised to take on Susan Collins

Delegates aligned with Jackson won the vast majority of the 500 slots that were up for grabs on Saturday and Sunday as Maine's 16 counties held two days of delegate selection for next weekend's state Democratic Party nominating convention. And Jackson's top rivals for the nomination backed him after dropping out of the race on Sunday.

Here are five things to know about the 58-year-old Jackson, a fifth-generation logger from Allagash, a sparsely populated town at the northern tip of Maine along the Canadian border.

Jackson first started in politics nearly three decades ago, protesting the entry of Canadian loggers who were entering the U.S. and being hired over Maine loggers. Jackson took part in blocking Canadian loggers from physically crossing the border into the U.S.

He ran for office in 2000 as a Republican, but was first elected to the Maine House of Representatives two years later as an independent.

Jackson joined the Democratic Party in 2004.

He was elected to the state Senate in 2008, and a decade later, when the Democrats won the majority, he became the chamber's president.

Jackson now strongly supports abortion rights and same-sex marriage. But as late as 2010, he received a perfect score from Maine Right to Life, a pro-life group. And in 2009, he voted against legalizing same-sex marriage in Maine.

Jackson attributed his conservative stances on the key social issues to his Catholic upbringing in rural Maine.

Balancing out his past votes against same-sex marriage and abortion rights, Jackson pointed to the Democratic Socialists of America and said, "People in the DSA think that I'm very progressive."

Jackson last year launched a campaign for the Democratic gubernatorial nomination in the race to succeed term-limited Democratic Gov. Janet Mills in the blue-leaning but competitive state.

Running on a platform of expanded healthcare and childcare, Jackson's gubernatorial run was endorsed last autumn by progressive champion Sen. Bernie Sanders of Vermont.

Jackson ended up finishing third in the ranked-choice Democratic primary for governor.

Jackson and Platner appeared together on stage with Sanders at rallies last year and this spring.

And late in the gubernatorial campaign, Jackson was endorsed by Platner, who at the time was cruising toward the Senate nomination. And Jackson backed Platner.

While Jackson was among those who quickly called on Platner to end his bid in the wake of the rape allegation, he made the case that he was the best candidate to continue the fight for a progressive and populist agenda.

Jackson, similar to Platner, is running on a progressive and populist platform aimed at working-class voters. He backs raising taxes on billionaires, the universal healthcare system known as "Medicare-for-all," abolishing U.S. Immigration and Customs Enforcement, and he opposes military aid to Israel at a time that Democrats are increasingly divided on support for America's longtime Middle East ally.

"This movement has always been bigger than one person. It's about taking on a system rigged against working people, fighting for 'Medicare-for-all,' strong unions, higher wages, reproductive freedom, and an economy where billionaires and corporations finally pay their fair share," Jackson said last week during a virtual town hall, as he pointed to Platner supporters.

At last week's debate among the Senate replacement candidates, Jackson pointed to Platner and said, "That's the thing that I think Graham did the best: talked about fighting against the healthcare industry and the prescription drug industry to make sure that people in this state and this country have affordable, quality healthcare."

Rep. Ro Khanna of California, a leading progressive in the House and a potential 2028 Democratic presidential contender, was a top Platner backer.

Khanna quickly moved his support to Jackson in this month's sprint to succeed Platner.

Also backing Jackson is Our Revolution, the group born in 2016 out of Sanders' first presidential campaign.

And Jackson enjoyed strong support from labor unions in Maine.

Support from Platner's former allies helped Jackson capture the overwhelming majority of county-selected delegates over the weekend.