You know them when you see them behind the wheel of that car on the highway that can’t seem to stay between the white lines.

You used to think: Can that driver really be drunk at 10 a.m.?

Now you think something else, and you’re probably right.

Thirty-five percent of drivers said they’ve read or sent a text message while driving in the last month, according to a new survey. Sixty-seven percent said they talked on a cellphone while driving in the past month, and almost a third said they do it regularly.

But virtually everyone agrees that dealing with text messaging and cellphones while driving is a serious threat to their safety, according to the same survey, conducted on behalf of the American Automobile Association Foundation for Traffic Safety.

It isn’t the first survey to shed light on the contradiction between what Americans do and what they think is right, but the percentages are particularly striking. Ninety-five percent of drivers consider text messaging as a serious threat, while 88 percent feel the same way about cellphone use.

This latest survey, based on a sampling of 3,147 driving-age people, is cause for both joy and frustration for U.S. Transportation Secretary Ray LaHood, who has crusaded against distracted driving since he was appointed in 2009.

“In just two-and-a-half years we have raised this issue to a level that it took drunken driving and seat belts and other safety issues much longer to do, and they had bigger budgets,” LaHood said Tuesday. “We’ve done all this just by using the bully pulpit. We’ve got the car companies’ attention. We’ve got the public’s attention. We’ve got law enforcement’s attention. But the bottom line is we have a long way to go to convince people to put their cellphones and their BlackBerrys in the glove compartment when they’re driving.”

The National Highway Transportation Safety Administration says that 5,474 people were killed and an estimated 448,000 were injured in 2009 in accidents that involved distracted driving. NHTSA said that accounted for about 16 percent of all traffic deaths.

The survey data seemed to suggest that drivers who use text messaging or cellphones while driving believe that other users pose a bigger danger than they do. Eighty-seven percent supported laws against sending or receiving text messages while driving. Seventy percent wanted laws against the use of hand-held cellphones, and half of those surveyed said all cellphone use should be outlawed while driving.

Thirty-four states, including Virginia and Maryland, and the District have laws that ban the sending and receiving of text messages while driving. Nine states, including Maryland, and the District require the use of hands-free hardware by drivers talking on cellphones.

Changing driving habits always has been difficult.

Two of the biggest campaigns in the past 50 years — against drunken driving and for seat belts — took years to get off the ground. The seat-belt campaign foundered when it was exemplified by the popular but ineffective jingle “Buckle up for safety!” Compliance began to take hold when the message was changed to “Click it or ticket.”

Similarly, it took decades of effort by Mothers Against Drunk Driving to toughen drunken driving laws and enforcement before the tide began to turn.