Democrats in Louisiana have always touted what they call the “30-30 rule” in statewide elections – meaning that to win, they needed 30 percent of the electorate to be black and they needed to get 30 percent of the white vote.

But exit polls in Tuesday’s Senate race show that the 30/30 rule is no longer a formula for Democrat success, because one half of that rule doesn’t look like it’s realistic anymore.

Specifically, Mary Landrieu didn’t get the 33 percent of the white vote she received in 2008. Nor did she get the 30 percent of the white vote the 30/30 rule would require.

Instead, Landrieu only got 18 percent of the white vote.

Just 18 percent.

She is in such poor odor with white voters that among white women – the demographic subset she occupies – she managed just 22 percent. Among white men she got just 15 percent on Tuesday. Bill Cassidy got 59 percent of the white vote and Rob Maness got another 19 percent.

Rob Maness got more white voters than Mary Landrieu did, according to the exit polls. He did this with $2 million raised and spent compared with nearly $14 million raised and spent by Landrieu – not to mention another $11 million spent on her behalf by third-party groups.

Landrieu’s turnout machine did get the black vote to 30 percent of the electorate, which more closely reflects a presidential cycle turnout model rather than the 27-28 percent one usually expects in a statewide cycle or the even lower figures of a midterm cycle. And Landrieu managed to pull 94 percent of the black vote that resulted (Cassidy had three percent, and Maness just one percent). National exit polls show that Republicans managed 10 percent of the black vote, meaning Louisiana is actually lagging.

The lesson of that last set of statistics is that with an entire month of Elbert Guillory’s ads on TV and the operations of the Black Conservative Fund on the ground and elsewhere, there is a metric in place with which to judge improvement. Anything above six percent of the black vote in December would be evidence that whatever is being done to produce it ought to be intensified in future races.

But with the 64 percent of the population made up of persons of pallor, Landrieu is largely dead in the water – particularly when she insinuated, and then doubled, tripled and quadrupled down on the statement, that white folks in Louisiana are a bunch of racists. That made the 30/30 rule inoperable.

Some quick math indicates that Landrieu’s 42 percent showing on Tuesday was more than two-thirds black (94 percent of the 30 percent black share of the vote is 28 percent, while 18 percent of the 64 percent share of the white vote is 11 percent). If that is the Democrats’ base electorate at this time, it seems impossible to imagine a Democrat could win a statewide race in Louisiana again under current circumstances.

It is almost certain that the electorate in December will be more white and conservative than it was on Tuesday. A runoff electorate always is, historically speaking.

And if Landrieu can’t claim more than 18 percent of the white vote she’s going to struggle to get to the 42 percent showing she had on Tuesday.

If you’re looking for a reason why the Democrat Senatorial Campaign Committee canceled $2 million of television ads on Landrieu’s behalf yesterday, this could well be your reason.