(CBS News) NEW YORK -- This year's presidential race is expected to be the most expensive ever.

The campaigns and their supporters will spend billions of dollars on television ads before it's all over.

Longtime Republican strategist Frank Luntz, a pollster and communications specialist, has studied hundreds of political TV spots.

He says most don't work.

"You get about 20 percent that actually help the candidate that they're designed to support," Luntz observed on "CBS This Morning." "Twenty percent turn people off -- and that's what's amazing about this -- because they don't understand the ad, it's too complicated, it's too gimmicky. And so, the person watching it actually ends up supporting the other candidate."

To determine whether an ad will hit the spot, media companies bring people into rooms and measure their response.

"We use something called 'instant response,' Luntz explains."And (people sitting in a room) react on a second-by-second basis. The dial is about the size of a remote control. They turn it up to every word, every phrase, every visual. And so, we can figure out, second-by-second, the exact moment when something either works, impacts them, or turns them off."

Full coverage: Election 2012

Luntz showed examples of ads taking on both President Obama and his presumptive GOP rival, Mitt Romney. Both, he said, have their intended impact.

Both used their own word against them, showing actual statements they made that their foes would feel came back to haunt them.

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Anatomy of attack ads that work - or flop