Story highlights Obama approval rating drops 8 percentage points over the past month

Lowest rating in more than 18 months, according to a CNN/ORC International survey

Drop fueled partly by a plunge in support from younger Americans

Obama has been dealing with controversies while priorities stall, job market sluggish

It's a glaring number in a national poll that's making headlines.

President Barack Obama's approval rating dropped 8 percentage points over the past month to 45%, the president's lowest rating in more than 18 months, according to a CNN/ORC International survey released on Monday.

And Obama's disapproval rating soared 9 points to 54% since mid-May.

Even more surprising: The overall decline in his approval rating was partially fueled by a plunge in support from younger Americans, a huge base of Obama's support.

Last month, nearly two-thirds of those in the 18-29 age group gave the president a thumbs up. His approval rating among that bracket fell 17 points in Monday's poll and now stands at 48%.

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The CNN/ORC International survey was conducted last Tuesday through Thursday.

It comes as the White House has been dealing with controversies over a government surveillance program; IRS targeting of tea party and other conservative groups; continuing fallout over the deadly terror attack on the diplomatic compound in Benghazi, Libya; and the Justice Department's secret collection of journalists phone records as part of a government investigation into classified leaks.

So what's behind the dramatic shift of younger Americans, who along with nonwhite voters had been the most loyal part of the Obama coalition?

"One explanation may be that younger Americans are more likely to feel they are personally affected by the surveillance programs," said CNN Polling Director Keating Holland. "More than half of all senior citizens, for example, think that the government has not collected their personal information, and since older Americans are less likely to use the Internet, they may be right. Among younger Americans, two-thirds believe that the federal government has gathered their personal data."

Julian Zelizer, a Princeton University professor and CNN contributor, said the shift isn't all about scandals but goes deeper.

"Part of it is probably that for younger people, the surveillance story is not a scandal but a sign the promise of 2008 was not fulfilled -- they see this and say he didn't do what he said he was going to do," Zelizer said.

"Part of this is a frustration in the gridlock in Washington. It's not just the scandals but the sense that nothing is going to get done. (Obama) hasn't been able to change Washington in that way. Instead of dealing with immigration or jobs, we're dealing with IRS and surveillance," he said.

"People in that age group are also struggling with jobs," Zelizer added. "That's a constituency is easy to disappoint."

Holland said that shows up in the "honest and trustworthy" category.

"Today, there are only minor differences between older and younger Americans on that measure, but a month ago, two-thirds of younger Americans considered Obama honest -- at least 10 points higher than any other age category. So maybe one reason why Obama fell so far with younger Americans is that he had farther to fall," he said.

So has Obama lost the under-30 crowd?

John Geer, chairman of Vanderbilt University's political science department, said probably not, but he could.

"I suspect the things that favor the Democrats will trump this in the long run," Geer said. "The youth wants to see more tolerance and more inclusion. While the youth has been favoring the Democrats in the past few years, neither (party) should see the partisan leanings of this group as set."

Zelizer agreed that it's too soon to look at the plunge for bigger implications.

"Democrats should see this as their warning -- they don't have to read this as a long-range trend," he said. "This immigration bill is still there, that's his chance. Get that bill through. It's not just about rhetoric and ideas but actual policy and change."