In a state-by-state roll call of delegates on the convention floor in Tampa, Florida that reflected the results of the Republican primary elections, Romney soared past the 1,144 threshold needed to formally earn the nomination.
The process removed any shadow of doubt that the man who will take on President Barack Obama in the November election could face a last-minute challenge.
The 65-year-old multi-millionaire businessman will formally take up the nomination with his all-important acceptance speech on Thursday, the climax of three days of rousing convention addresses by party grandees and rising stars.
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Romney lies neck-and-neck with Obama in national polls 10 weeks before an election that should be his for the taking, given the sour economy and an unemployment rate that is lingering stubbornly above eight percent.
The Republican hopeful flew to Tampa two days early to attend an opening night of speeches headlined by his wife Ann's attempt to capture the lighter side of a candidate who has struggled to connect on a human level with many voters.
The convention kicked off earlier Tuesday with the usual blend of political theater and razzmatazz despite the hurricane bearing down on New Orleans that derailed Monday's opening and still threatens to cast a pall over proceedings.
The storm presents the candidate with a tricky challenge as he must tread a fine line between driving home his political message and showing sensitivity to voters in harm's way.
Many Americans do not tune in until the convention season starts -- Obama and the Democrats hold theirs next week in Charlotte, North Carolina -- so Tampa provides Romney with a golden opportunity to reintroduce himself.
The run-up to the convention was marred by incendiary remarks from Todd Akin, a Republican congressman seeking a Senate seat in Missouri, who suggested women's bodies spontaneously prevent pregnancy after a "legitimate rape."
The Romney camp, which roundly condemned the remarks, is keen to get back on message, pressing the case that the successful businessman understands the economy better than Obama and knows how to get the country back on track.
Obama will break with tradition and campaign hard through his rival's event, countering Romney's bid to grab an uninterrupted chance to make his case.
Forecasts put Hurricane Isaac on a direct path to hit New Orleans overnight, seven years to the day after Hurricane Katrina devastated the city and killed 1,800 people in one of the country's worst-ever natural disasters.
