Republican presidential candidate Mitt Romney speaks during his debate with US President Barack Obama.

Story highlights

Ahead of the debate twice as many voters expected Obama to win, a poll showed

The polls afterwards turned that expectation upside down: Majority of voters said Romney won

Fisrt presidential debate delivers a much needed boost to Romney's campaign

CNN  — 

Mitt Romney was ready.

After nearly two-dozen debates against fellow Republicans earlier in his campaign and exacting preparation in the months since, the Republican candidate had his first chance to debate with Barack Obama face-to-face. The result seemed so imbalanced that even some of the president’s supporters quickly conceded defeat.

Complete coverage: Presidential debates 2012

“It looked like Romney wanted to be there and President Obama did not,” said Democratic Party strategist and CNN Contributor James Carville.

Romney has been trailing in many opinion polls. Some fellow Republicans have criticized his campaign for lacking focus and Romney himself for committing a series of gaffes. The three scheduled debates with Obama leading up to the November 6 election have been widely described as his best chance to change course.

Read more: Romney shakes up the race

There were no attention-grabbing insults or errors in the 90 minutes the two men spent on stage in Denver, Colorado. There was no single moment that will dominate how voters are likely to remember the conversation.

But Romney seemed cheerful, confident and in command of his facts, challenging the president at every opportunity and promising voters he could do better.

“My priority is putting people back to work in America. They are suffering in this country,” he said. “Going forward with the status quo will not cut it for American people struggling today.”

Read more: Five things we learned from the presidential debate

Obama hasn’t had to endure a televised debate since he was elected four years ago and aides said the demands of office prevented him from devoting as much time as Romney to preparing.

The president seemed tense for much of the debate, smiling tightly and showing little of the passion or energy that he has summoned for so many of his public appearances.

Read more: 10 debate moments that mattered

The impact was obvious from our polling. The percentage of Americans who said ahead of time they expected Obama to win the debate was twice as high as the ones who thought Romney would prevail.

CNN’s first poll afterwards found that expectation was turned upside down. Voters who saw the debate said Romney won it, by a margin of more than two to one.

Obama and Romney will meet two more times and their vice-presidential running mates are scheduled to debate each other next week as well.

A debate won’t necessarily decide the election, but Romney’s campaign badly needed a boost, and this week it got one.

The opinions expressed in this commentary are solely those of Jonathan Mann.