For New Jersey, Christie said, his leadership meant taking on teachers' unions, saving billions of dollars in reforming the public pension system, and delivering balanced budgets that lower taxes. (Neither property taxes nor income taxes are actually down in the state, however, despite some business-tax cuts.)
For the country, Romney's leadership would mean ending President Obama's health-care overhaul, rolling back the national debt, and "telling seniors the truth about our overburdened entitlements."
"Mitt Romney will tell us the hard truths we need to hear to put us back on the path to growth and create good-paying private-sector jobs again in America," he said.
Moments earlier, the convention had roared its approval when Ann Romney said of her husband, "This is the man America needs. This man will not fail," whereupon the nominee stepped onto the stage and kissed his wife, to the crowd's delight.
Christie's speech featured themes and anecdotes the popular governor had delivered before. But it had a grander scope, with lines about "taking our country back" and ushering in a "second American century."
His words, such as "bipartisan compromise," were largely positive, more so than expected from a governor known for confrontation. There was even gentle advice directed at his own party.
The crowd grew increasingly excited as Christie spoke, culminating in a dramatic moment when he asked the crowd to stand - literally - for Romney.
"It's the power of our ideas, not of our rhetoric, that attracts people to our party," he said. "We win when we make it about what needs to be done; we lose when we play along with their game of scaring and dividing."
Christie mentioned "absentee leadership in the Oval Office," but he never uttered these two words: Barack Obama.
"You see, Mr. President - real leaders don't follow polls," he said. "Real leaders change polls."
Romney's name came up, of course - but only seven times in more than 2,500 words. The speech was more oriented around Christie and the Garden State.
He name-dropped a Bruce Springsteen song and bounded onto the stage following a video depicting him hanging with kids and saying words like "hell."
A gregarious and relaxed Christie opened with his family history. He told of his Irish father - who watched with pride from a luxury box at the Tampa Bay Times Forum. And he told of his late Sicilian mother - a tough woman raised by a single mother who in turn ended up having to raise her two younger siblings.
"She spoke the truth - bluntly, directly, and without varnish," he said. "I am her son."
And with that big applause line, Christie was off, moving his hands, raising his eyebrows, and smirking out of the side of his mouth to accentuate points.
For the thousands of delegates gathered before him in red, white, and blue, Christie morphed from the small screen of YouTube clips, where he invokes phrases rarely uttered by elected officials ("Get the hell off the beach!"), to several huge screens throughout the arena.
When he talks about his mother, he said in an interview this week, audiences can relate to him and understand his gruff, funny, truth-telling personality.
"The greatest lesson Mom ever taught me, though, was this one: She told me there would be times in your life when you have to choose between being loved and being respected," he said. "She said to always pick being respected, that love without respect was always fleeting but that respect could grow into real, lasting love.
"Now, of course, she was talking about women."
That was the only big laugh line from a speaker who often triggers several belly laughs, but it served to pivot to the thrust of his remarks.
He said being respected "applies just as much to leadership."
"I believe we have become paralyzed by our desire to be loved," he said. That's why "hard truths" need to be said.
Long before the speech began, Democrats blasted Christie for his record in New Jersey and alleged that he has a single-minded quest for national fame.
"It's been a terrible comedy of failures in New Jersey under his leadership," Sen. Frank Lautenberg (D., N.J.) said in a conference call with reporters earlier in the day.
The keynote was seen as something of an audition for a possible presidential run. But first, he has a reelection next year to consider.
During the speech, State Assemblyman Louis Greenwald (D., Camden), a possible gubernatorial candidate, tweeted point-by-point responses.
Another likely gubernatorial contender next year, State Sen. Barbara Buono (D., Middlesex), published a piece in Politico on Tuesday. She cited New Jersey's higher-than-average unemployment rate and other poor economic indicators to say Christie was misleading the public with recent boasts of a "New Jersey comeback."
That phrase did not make it into the speech, but he directed return fire of his own, saying Democrats think Americans "want to be coddled by big government."
His first standing ovation came with this line about Democrats: "They believe in teachers' unions; we believe in teachers."
Because of the threat of Isaac, Tuesday was the first real day of the convention. Despite a mini-revolt from supporters of U.S. Rep. Ron Paul of Texas, a former presidential candidate, the day went smoothly, unlike the more rough-and-tumble conventions of the past.
In the afternoon, a representative from each state stood to formally deliver delegate votes to Romney. When New Jersey came up in alphabetical order, its 50 votes put Romney over the top, giving him enough to secure the nomination.
New Jersey's votes were delivered by Christie's brother, Todd, a delegate.
The theme of Tuesday's convention was "We Built It," a response to part of a recent Obama speech in which he suggested that business owners need government, from road builders to teachers, in order to thrive.
Between each speaker who blasted Obama for these words, videos aired depicting small-business owners similarly infuriated.
Ann Romney, meanwhile, spoke of the struggles and pride of being a woman. Republicans have faced criticism as starting a "war on women," and her words sought to defuse that.
"I love you women!" she said. "And I hear your voices."
She added: "You are the best of America. You are the hope of America. Tonight we salute you and sing your praises."
By contrast, Christie's goal was not to appeal to a certain segment, he said this week. It was intended to lay a foundation for the future of the Republican Party.
"If you're willing to hear the truth about the hard road ahead, and the rewards for America that truth will bear, I'm here to begin with you this new era of truth-telling," he said.
Contact Matt Katz at 609-217-8355 or email@example.com, or follow on Twitter @mattkatz00. Read his blog, "Christie Chronicles," at www.philly.com/christiechronicles.