Perhaps: Ad spending.
Per Professor Ken Goldstein, director of the University of Wisconsin-Madison’s Advertising Project:
Fundamental factors matter most in elections and advertising is likely to have fairly modest effects at the margin. That said, unbalanced flows of paid information in a generally positive free media environment have the greatest potential to move numbers and influence races. This was the environment between February 5 and February 19 and that is what won Barack Obama the Democratic nomination.
Not that anyone, technically, has yet won it. But that’s Goldstein commenting on the Ad Project’s recent findings (they analyzed numbers compiled by TNS Media Intelligence/CMAG) that in states with primaries from February 5-19, Obama out-advertised Clinton on TV by a “sizable margin” (3 to 2 on the low end, 5 to 1 on the high end) and won nine straight contests netting 118 delegates in this time frame. In Maryland and Virginia, per the report, “Obama had the airwaves all to himself for 7 out of 12 days. Since local media — especially television news —often cover the air war, Obama likely got an added boost of free media coverage of his ads during this time as well.”
Other tidbits from the report:
An estimated nearly $200 million has been spent on presidential campaign TV ads to date (including all candidates and outside groups): Obama has spent some $75 million; Clinton has spent just over $46 million; and McCain has spent $11 million.
The top issue for Democratic presidential candidates has been health care. For both the Clinton and Obama campaigns, the most talked about issue in their campaign advertising has been health care. Republican presidential candidates have generally focused on the issues of taxes, immigration, and abortion in their campaign advertisements.