A review of the Texas vote shows that among the 15 counties Mr. Obama won with his biggest margins, the voter falloff between the president and Senate races ranged from 22 percent, in Harris County, to 38 percent, in Jefferson County. (c-tree: Voter falloff is the tendency of the voter to vote only for a presidential candidate and ignore the downticket choices. This is believed by the authors to reflect the likelyhood of the voter either not returning in the fall if their choice loses or of crossover voters not wanting to support downticket Democrats)
The biggest falloff was in Republican-heavy Collin County, which Mr. Obama carried by 55 percent. Four in 10 Democratic voters who cast ballots in the presidential race didn't vote in the Senate race.
Republican strategist Royal Masset said the Collin County vote illustrates a big reason for the voter falloff – Republican crossover voters who wanted to influence the outcome.
Although some conservative talk show hosts had urged Republicans to cross over and vote for Mrs. Clinton in order to keep the contest going, there was little evidence that happened.
According to exit polls, only 9 percent of Democratic voters statewide identified themselves as Republicans, and they went for Mr. Obama, 53 percent to 46 percent.
Republican pollster Mike Baselice said a 9 percent to 15 percent crossover vote is typical in Texas, and early-voter analysis indicates many of the "new" voters had some history of voting Democratic in general elections and were only new to a primary.
On the Clinton side, her top 15 counties had a substantially lower voter falloff, from 11 percent in Webb County to 24 percent in Bowie County and 26 percent in Hidalgo County.
In South Texas, a Clinton stronghold, more people likely voted for both president and Senate because of the presence of a Senate candidate with a Hispanic surname.
Removing the South Texas counties from the equation did not significantly change the falloff numbers.