PORTLAND — On a rain-slickened patio above a bustling diner, Maine Gov. Paul LePage on Wednesday morning became the first Republican governor in the nation to endorse a presidential candidate for 2016: Gov. Chris Christie of New Jersey.

LePage described Christie as a mentor and a friend and thanked him for his support during a tough re-election fight in Maine last year, when as head of the Republican Governor’s Association Christie came to Maine four times to stump and fundraise for LePage.

Those stops included one at Becky’s Diner, where the duo returned on Wednesday. Many patrons seemed surprised to see the noted governors and the swarm of local and national reporters and cameramen behind them, who jammed the diner’s packed, narrow aisles. Waitresses elbowed through the throng, bringing plates to and from the kitchen.

Christie and LePage shook hands and exchanged pleasantries with a handful of customers before making their way upstairs to a rooftop deck for a news conference, where LePage announced his endorsement.

“When all of you and your colleagues around the country had me as a dead-walking governor, Chris Christie had faith,” LePage told members of the media. “He believed in us, came up, supported me wholeheartedly, never batted an eye.”

According to campaign finance reports, the RGA under Christie’s watch spent $5.1 million to help re-elect LePage in 2014, the most spent by any group on any candidate in Maine that year.

“I think he’s the real deal,” LePage later added. “He’s been a governor. He knows what hard decisions are. He’s going to make them. He’s not going to be a politician and talk out of both sides of his mouth. He’s going to tell you things you may not want to hear, but you need to. Then he’s going to go to work trying to fix them.”

Wednesday marked Christie’s first full day as a 2016 Republican presidential candidate. Portland was his first stop before traveling to New Hampshire, site of the nation’s first presidential primaries, for a schedule packed with public and private events throughout Independence Day weekend.

Christie said he was honored to have LePage’s endorsement because he and LePage are cut from the same cloth — no-nonsense conservatives elected to run largely Democratic states.

“In the first full day of my presidential campaign, to be able to come up here and receive an endorsement from somebody who knows what it’s like to run a blue state, knows what it’s like to make tough decisions, knows what it’s like to engage in hand-to-hand combat to try to get things done for the people that elect you — to get an endorsement from Paul LePage today is an incredible honor for me,” Christie said.

Christie’s occasional bipartisanship in Democrat-leaning New Jersey and his decision to expand Medicaid in his state, a key pillar in Democratic President Barack Obama’s health reform law, have earned him scorn from conservatives in the past. Backing from LePage, whose conservative bona fides are unassailable, could help Christie win over those conservative voters, who are a powerful force in Republican primary elections.

Christie, who like LePage is known for a brash style adored by supporters and scorned by opponents, once was viewed as a front-runner for his party’s nomination in 2016.

That status has been diminished, partly because of the entrance of high-profile Republicans such as former Florida Gov. Jeb Bush into the race, and the “Bridgegate” scandal of 2013, when Christie aides orchestrated the closing of approach lanes for the George Washington Bridge connecting New Jersey and New York City, the busiest bridge in the country, which critics described as an act of retribution against a Democratic New Jersey mayor.

Christie has claimed no knowledge of the closures and a federal judge in New Jersey on Monday dismissed a class-action lawsuit filed by people stuck in traffic in the bridge lane closings.

LePage also is no stranger to controversy. The Maine governor is under scrutiny from members of both parties in the Legislature, some of whom have filed requests for an investigation into alleged abuses of power. There are many voices in the Legislature and electorate calling for impeachment.

Most of the heat is centered on LePage’s threat to cut state funding to a charter school operated by Good Will-Hinckley, a Fairfield-based nonprofit, if the group were to follow through with hiring House Speaker Mark Eves, a Democrat, as its new president. Good Will-Hinckley fired Eves who accused LePage of blackmail. Eves is considering suing the governor.

Christie brushed aside criticism of LePage’s actions, saying LePage made a “difficult decision” in the best interest of Maine students.

“I support the governor’s stand that he’s taken on this,” Christie said. “As with most things, controversies come and go. Leadership is what stands strong and firm. That’s what this governor has stood for throughout his time in office.”

After Christie climbed into his sport utility vehicle, leaving Portland for New Hampshire, Democrats lobbed salvos at the two governors, describing them as twin symbols of controversy and corruption.

“The first major endorsement Gov. Christie receives after announcing he’s running for president is from a governor who is facing impeachment threats for his role in exacting retribution upon a political adversary. Can’t say we’re surprised,” Kaylie Hanson, a spokeswoman for the Democratic National Committee, said.

Maine Democratic Party Chairman Phil Bartlett said Christie must be “desperate” to stand beside LePage.

“Gov. LePage has alienated state lawmakers, his constituents and members of his own Party as he faces growing calls for impeachment and investigations,” Bartlett said. “It’s equally fitting that the only person in Gov. LePage’s corner is Chris Christie of ‘Bridgegate’ fame.”

Christie said those who ascribe meaning to his appearance with LePage or compare their brash impolitic reputations should come to only one conclusion.

“I’m going to be who I am, and that’s why Paul’s with me. That’s why Paul’s had the success he’s in Maine,” he said. “This is a guy who knows how to make decisions.”