Updated at 3:15 pm

Mitt Romney cast the American public in a pessimistic mood in his acceptance speech to the Republican National Convention on Thursday night. He said:

"But today, four years from the excitement of the last election, for the first time, the majority of Americans now doubt that our children will have a better future."

Several recent public opinion polls support the basis of Romney’s claim; less than half of the public is currently optimistic about  the economic security of future generations. But this lack of optimism is not something new.

First a rundown of the current data. A Pew Research Center poll from July finds 42 percent saying that “when your children are the age you are now” their standard of living will be better.

A Bloomberg poll in June finds 45 percent of the public expects children to have a lower living standard in the future than their parents have today. Just 28 percent expect it to be better.

An NBC/Wall Street Journal poll from May reports that 63 percent are not confident “that life for our children's generation will be better than it has been for us.”

Each example supports Romney’s assertion of low optimism “that our children will have a better future.” Contrary to Romney’s statement, the finding is nothing new.

The Pew question is based on a trend from the General Social Survey that dates to 1994. In Pew data from 2008 to now, fewer than half have expected children to do better. Optimism was higher in the GSS data from 1998 to 2010, but it dipped as low as 45 percent in the mid-1990s.

A Gallup poll from April 2011 does find a breaking point on a similar question with 44 percent saying it is very or somewhat likely that "today's youth will have a better life than their parents" and 55 percent saying that it is unlikely. That result is the first time a majority expressed such pessimism in polls going back to 1983.

The trend from NBC/Wall Street Journal shows more consistently negative opinions than the Pew/GSS trend. Since 2009, more than six in 10 have lacked confidence that the next generation’s future will be better. It was as high as 68 percent in 1993.

Regardless of whether this lack of optimism is a new opinion for the public, Romney has not yet made the case that he as the answer for the country’s economic future.

In a Washington Post-ABC News poll released this week, 55 percent say they are either “not so” or “not at all” confident that Romney could quickly get the country back on economic track if he were elected. People are just as suspect that Obama can turn things around if reelected.