In the latest NBC / Marist Poll of the state of Virginia, released 05/24/12, Mitt Romney has a nominal 1-point advantage over Barack Obama among home-phone (landline) respondents, but Obama leads Romney by 18 points among cell-phone respondents, a 19-point difference between cell-phone and home-phone respondents.
When the two populations are proportionally blended, Marist reports that Obama is 4 atop Romney in Virginia, 48% to 44%.
Marist found a 26-point difference between cell-phone and home-phone respondents in Florida on 05/24/12. SurveyUSA found a 15-point difference between cell-phone and home-phone respondents in North Carolina on 05/22/12.
A majority of the state election polls released in 2012 still do not make a special effort to contact cell-phone respondents. Of those opinion pollsters who do include cell-phone respondents, only two pollsters routinely crosstab how cell-phone and home-phone respondents vote, providing a key window into the electorate, and spotlighting how potentially lopsided those polls without cell-phone respondents can be.