WASHINGTON —  The cell-phone-only crowd is not yet large enough and their views not different enough to affect the accuracy of traditional political polling, a new study suggests.

Not yet, anyway.

The report, based on polling by the Pew Research Center and The Associated Press, reaffirmed that those with only a cell phone tend to be younger, less affluent, more likely to be male and more likely to be minorities.

But when the responses to a series of political questions from those with only cell phones were blended in with the rest of those reached on traditional landlines, results were not affected. Very small differences in the results virtually disappear when the cell phone sample is blended together, and weighted to match the demographics of the national population.

This is consistent with an AP-Pew poll done earlier this year and other surveys.

About one in 10 adults in this country have only a cell-phone, based on projections of growth from research, including that done by the Centers for Disease Control and Prevention. Research done during the CDC's National Health Interview Survey suggests the number of cell-phone-only households has been growing by about 1 percentage point every six months over the last few years.

The growth of the cell-phone-only group has raised concerns among survey researchers that it would render obsolete the most commonly used polling method of contacting a random sample of the public on traditional landline phones.

Growth of the cell-phone-only group may eventually reduce their differences from the overall population, said Scott Keeter, a survey researcher at the Pew Research Center.

The biggest differences found between landline phone users and cell-phone only users involved their levels of political engagement.

Just 49 percent of the cell-only users were registered voters, while 78 percent of those in the landline sample were registered voters. That's another reason the cell phone only group has a minimal effect on political polling.

The study was based on a poll of 2,004 adults, including 1,804 with traditional landlines and 200 with only cell phones. The registered voter sample included 1,503 registered voters with landlines and 97 registered voters with only cell phones. The poll was conducted from Sept. 21-Oct. 4 and had a margin of error of plus or minus 3 percentage points for both samples, adults and registered voters.