"All he has to do is go out there and tell the truth. If you tell the truth about what's going on in our country, people are going to understand," Christie said on ABC's "This Week" on Sunday.
Christie said if he were confronted with the claims of an Obama ad that says Romney will cut taxes for the wealthiest earners and nix regulations on Wall Street, he would say: "Stop lying Mr. President."
He called Obama a "very good" debater and expects him to perform well on Wednesday night, given his four years in the White House.
"But he can't change the facts and that's going to be a problem for the president," he said.
Democratic strategist David Plouffe strongly denied the Republican accusations that the president is skewing the facts, saying the GOP is using the rhetoric to raise expectations for the debate and its potential to fundamentally change the trajectory of the presidential race.
Plouffe said the president isn't worried about fact-checkers, adding that perhaps the Romney campaign should take a look in the mirror and realize that that voters simply don't like the Republican's ideas.
"People don't want to go back to the same trickle-down policies that caused the recession in the first place," Plouffe said.
The president will stick to the facts about "where we are as a country and where we need to go how we rebuild an economy that makes the middle class secure, and with great detail so people understand if this president get reelected what he's going to for them, for the middle class."
Christie dug in about Romney's tax policy, arguing that while it may lower tax rates for higher-income taxpayers, the plan would eliminate deductions and loopholes that would leave most in the upper brackets paying "just as much as they pay today."
That includes eliminating significant deductions and loopholes "so no one is paying less in the wealthy class than they were before."
But Plouffe argued that Romney's doesn't have a deficit plan. "He has a plan to cut taxes for millionaires and billionaires," Plouffe said
The New Jersey governor also criticized the president for failing to reach common ground with congressional Republicans on ways to jump start the economy, a trait, he argued, that Romney learned while governor of Massachusetts.
"The president has never learned what Romney knows," Christie said.
"You can lay out aspirational goals and visions, but then you got to get down to negotiating with people to get things done," he said.
"In Washington, D.C., the president draws hard lines and doesn't ever know how to negotiate and compromise that's why we're in the gridlock we're in today."
Christie, who kicked off the Republican convention last month and was once considered a choice for vice president, said he expects Romney to shake things up Wednesday and is confident the tide will turn toward the Republican candidate.
"Every time Mitt Romney has been confronted in this campaign with one of these moments, he has come through in the debate and performed extraordinarily well, laying out his vision very clearly and also contrasting himself and his vision with whoever his opponent was at that time," he said.
"So I have absolute confidence that when we get to Thursday morning all of you are going to be shaking your head, saying it's a brand-new race with 33 days to go."
Amid criticism from conservatives that the Romney campaign is playing it too safe to win, Christie expects "a big and bold performance" on Wednesday night that will perk up his supporters.
"I have absolute confidence in that," he said. "The ideas are there and this is the first moment voters will see these two guys side by side laying out their vision unfiltered.
"I think that's going to be a powerful moment for Mitt Romney," Christie said, adding that conservatives will "certainly be happier than they are now."