BOSTON - Acknowledging Monday that President Obama has seen a surge in voter support since last week’s Democratic National Convention, the Romney campaign’s pollster likened the bounce to a “sugar high” and argued that the Republican challenger has a long-term advantage over the president.

Neil Newhouse, Mitt Romney’s pollster and senior strategist, wrote a memorandum released to reporters to rebut the conventional wisdom that Romney has fallen behind in the presidential race and to calm any panic among supporters. In the memo, Newhouse wrote that Obama “has seen a bounce from his convention” but contended that the president’s approval ratings are likely to recede in the weeks ahead.

“Don’t get too worked up about the latest polling,” Newhouse wrote. “While some voters will feel a bit of a sugar-high from the conventions, the basic structure of the race has not changed significantly. The reality of the Obama economy will reassert itself as the ultimate downfall of the Obama Presidency, and Mitt Romney will win this race.”

According to several new national polls, after months of deadlock, Obama opened a lead over Romney after last week’s Democratic convention in Charlotte. In a Reuters/Ipsos poll released Sunday, 47 percent of likely voters supported Obama and 43 percent Romney. In a Gallup tracking poll, Obama leads Romney 49 percent to 44 percent, while an automated Rasmussen poll released Monday put Obama at 50 percent and Romney at 45 percent.

In his memo, Newhouse said that as more voters begin to understand the difficult economic data, they will turn against Obama.

“The key numbers in this election are the 43 straight months of 8% or higher unemployment, the 23 million Americans struggling to find work, and the 47 million Americans who are on food stamps,” Newhouse wrote.

He noted that the battlefield has expanded. Over the weekend, the Romney campaign began advertising on television in Wisconsin, a traditionally Democratic-leaning state, hoping to put the home state of GOP vice presidential nominee Rep. Paul Ryan in play. Newhouse also pointed to a new poll from the Albuquerque Journal showing a close contest in New Mexico, a state both campaigns have long believed would lean toward Obama.

But Newhouse did not mention Ohio, an all-important swing state where Obama appears to have an advantage. Nor did he refer to Michigan and Pennsylvania, two states the Romney campaign had hoped to court but where Romney and Republican allies have not been advertising.

Newhouse’s complete memo:

MEMORANDUM

TO: Interested Parties

FROM: Neil Newhouse, Romney for President Pollster

RE: State of the Race

DATE: September 10, 2012

Don’t get too worked up about the latest polling. While some voters will feel a bit of a sugar-high from the conventions, the basic structure of the race has not changed significantly. The reality of the Obama economy will reassert itself as the ultimate downfall of the Obama Presidency, and Mitt Romney will win this race.

In his acceptance speech, President Obama did not offer any solutions for the millions of Americans unemployed or underemployed. But his convention speech was not the only big letdown to voters, as Americans also dealt with yet another dismal jobs report last week. President Obama is the only president in modern American history to stand before the American people asking for re-election with this many Americans struggling to find work. The key numbers in this election are the 43 straight months of 8% or higher unemployment, the 23 million Americans struggling to find work, and the 47 million Americans who are on food stamps.