I found that a bit hard to believe, so I wrote to Dr. Sabato and received the following response (bolding added for emphasis):
Hello and thanks---That is clearly an exaggeration of what I have said to a couple of reporters in the last month or so. Here is what I have actually told them: Early in his political career, George Allen boasted of having entered the 1977 Democratic gubernatorial primary as a young Republican to vote for Henry Howell over Andrew P. Miller, because he viewed Howell as the weaker nominee in November. Howell won the primary narrowly and lost in a landslide to John Dalton in November. Allen was part of a semi-organized effort by Republicans to vote for Howell in the summer of 1977. Allen hasn+óGé¼Gäót forgotten that. From quite a number of my own confidential sources, I know that Allen and his people would much prefer to run against Miller than Webb. Maybe they are right that Webb is stronger, maybe they are wrong, but that+óGé¼Gäós what they think. Ergo, given Allen+óGé¼Gäós own precedent, which he surely remembers, and given Dick Wadhams+óGé¼Gäó talents as an organizer, I said I wouldn+óGé¼Gäót be surprised if the Allen folks quietly undertook such an effort. That is not a statement of fact, just a surmise. Thanks for checking, Larry SabatoDr. Larry J. Sabato
Director, Center for Politics
University Professor of Politics
University of Virginia
www.centerforpolitics.org
sabato@virginia.edu
The bottom line is this: Republicans badly WANT Harris Miller to be the nominee, and they MIGHT try some shenanigans on June 13, but it's certainly not a sure thing that they will. However, why take any chances? Fellow Democrats, let's NOT allow George Allen Republicans to mess up our primary! Get out there and vote for Jim Webb to show them that we want the STRONGEST candidate to run against George Allen this year, not the weakest.
I seriously doubt the Allen camp could mount a major GOTV effort for Miller and keep it quiet, so anything they do would be fairly small scale.
The extent to which the "hint dropping" on various conservative blogs and other right wing gathering places has a real effect is yet to be seen. It's possible that repubs could come out in force this way, but that would require individual motivation (as opposed to taking orders from the top).
The bottom line is that if the Webb supporters come out in force on primary day, Allen's [probable] manipulation of the system will fail. And so will his bid for a second term!
Democratic support is clearly behind James Webb on a grassroots, regional, statewide and national level. There is no denying Jim Webb will be the stronger candidate and has the support to make a better run against George Allen. We must not let Allen's supporters sabotage this election to steal another undeserved term. Therefore I ask you emphatically to please withdraw from this race. You will earn a lot of love form the Democratic netroots and grassroots, and you would serve to strengthen our chances of retaking the Senate.
If you don't withdraw, you could very well be ensuring the success of the man you seek to take a Senate seat from. Please consider my plea and do what is best to rid us of our current Senator. Be the gentleman and withdraw now.
Very Respectfully,
It happens all the time in states that allow crossover voting -- that's why parties in most states prefer voter registration by party and "closed" primaries.