[new article] Sept. 20: Obama's Convention Bounce May Not Be Receding http://nyti.ms/PGC1Qw
Sept. 20: Obama’s Convention Bounce May Not Be Receding
By NATE SILVER
President Obama’s position inched forward in the FiveThirtyEight forecast on Thursday. His chances of winning the Electoral College are 76.1 percent, according to the forecast, up from 75.2 percent on Wednesday. Mr. Obama’s projected margin of victory in the national popular vote also increased slightly, to 3.4 percentage points.
By and large, the story that Thursday’s polls told was the same one as on Wednesday. Mr. Obama continues to get very strong results in state polls that use industry-standard methodology, meaning that they use live interviews and place calls to mobile phones along with landlines.
In the 10 states that have generally been ranked the highest on our tipping-point list — Ohio, Virginia, Florida, Wisconsin, Colorado, Nevada, Iowa, Pennsylvania, New Hampshire and Michigan — there have been 21 such polls since the Democratic convention ended. Mr. Obama has led in all 21 of these surveys — and usually by clear margins. On average, he has held a six-point lead in these surveys, and he has had close to 50 percent of the vote in them.
Mr. Obama’s results have been more varied among polling firms that use different methodologies. A series of polls in eleven swing states, released on Thursday by the online firm YouGov, were fairly strong for Mr. Obama, putting him ahead among likely voters in all of the states except North Carolina.
But automated polls, like those from the Rasmussen Reports, have had lukewarm results for Mr. Obama. A Rasmussen Reports poll released on Thursday, for instance, put Mr. Obama three points behind in Iowa.
I don’t mean to keep repeating this point about polling methodologies, but it really does seem to be the easiest way to unpack the state-level data right now.
In contrast to the six-point lead Mr. Obama has held on average among the swing-state polls that included cellphones, and the five-point lead he had on average among the YouGov Internet surveys, Mr. Obama has been ahead by just two points on average in polls that called landlines only, most of which were “robopolls” conducted by automated script.
Nate Silver 
