After looking around for a while, I finally found one news source that’s focused on the existence or non-existence of African-American voters materializing to support Thad Cochran in today’s Mississippi GOP runoff: the New York Times’ The Caucus site. It sounds like “crossover” voting is real but limited, and it also appears poll workers are vigorously enforcing the ban on participation by those who voted in the June 3 Democratic primary:
JACKSON, Miss. — In the early afternoon, turnout continued to be relatively light in the black neighborhoods here. Some African-American voters showed up at polling places only to learn that they were ineligible to vote in Mississippi’s Republican primary because they had voted in the Democratic primary earlier this month.
Most polling locations reported single-digit turnout throughout the morning, though some representatives said that was considered high because usually almost no Republican voters show up.
At the Golden Key Activities Center in the Shady Grove neighborhood, 20 voters had cast ballots as of 11:45 a.m. local time, more than most other predominantly black precincts. But 12 others who showed up had been turned away at the door, the precinct manager said.
James Bennett planned to vote for Thad Cochran after black canvassers came to his door on Mr. Cochran’s behalf and asked for his vote. But when he arrived, he found out he was ineligible to vote because he had already voted in the Democratic primary.
He said with a laugh that he was not upset, and he planned to vote for the Democratic candidate Travis Childers in November.
So it doesn’t appear there’s any African-American crossover tsunami in the works. The question, however, is how the prospect of crossover voting might have affected turnout and even candidate preferences in white conservative areas.