Frisina, Herron, Honaker and Lewis have posted this paper that moves to the top of my “to-read” list. Here is the abstract:

The 2006 midterm elections in Florida have focused attention on undervotes, ballots on which no vote is recorded on a particular contest. This interest was sparked by the high undervote rate–more than 18,000 total undervotes out of 240,000 ballots cast–in Florida’s 13th Congressional District race, a race that, as of this paper’s writing, was decided by 369 votes. Using precinct-level voting returns, we show that the high undervote rate in the 13th Congressional District race was almost certainly caused by the way that one county’s (Sarasota’s) electronic touchscreen voting machines placed the 13th Congressional District race above the Florida Governor election on a single screen. We buttress this claim by showing that extraordinarily high undervote rates were also observed in the Florida Attorney General race in Charlotte and Lee Counties, places where that race appeared below the Governor race on the same screen. Using a statistical imputation model to identify and allocate excess undervotes, we find that there is a roughly 90 percent chance that the much-discussed Sarasota undervotes were pivotal in the very close 13th Congressional District race. Greater study and attention should be paid to how alternatives are presented to voters when touchscreen voting machines are employed.