I looked at the Gonzales (R) poll to get a sense of what Brown or Hogan would have to do in order to achieve a victory tomorrow. I’ll analyze the electorate from a racial prism because solid black turnout is critical to Anthony Brown’s chances.

Republican Gov. Robert Ehrlich’s 2002 victory rested in large part on unusually low African-American turnout–blacks composed an astonishingly low share of the electorate in that year. In 2006, the CNN exit poll indicates that African Americans were 23% of the electorate, a major increase from 2002.

Gonzales estimates black turnout this year at 25%, at the low end of predictions but not at all out of the realm of possibility in our state where African Americans comprise 28.1% of the voting-age population. Moreover, African Americans have formed a greater part of the electorate in presidential years since at least 2000.

Let’s assume Gonzales is right and blacks form only one-quarter of the electorate. The share of the white vote that Brown needs to reach 50% depends on the the percentage of blacks who support him. Gonzales reports that Brown possesses an 87-5 advantage among African Americans.

Exit polls indicate that Gov. Ehrlich gained 15% of the black vote in 2006, when he lost his bid for reelection. It seems unlikely that Hogan could do as well against Brown, who would be the State’s first African-American governor. If one splits the undecideds in the same 87-5 proportion, Hogan still has just 5% of the black vote. But let’s say Brown’s share could fall in the 5% to 10% range.

If blacks are 25% of the electorate and Brown receives 95% of their votes, then he needs just 35.0% of the (mostly white) non-black vote to win election–this is 10% less than O’Malley won in 2006. If Brown gets 9 in 10 of black voters, however, Brown needs 36.7% of non-black voters to reach 50% of the total vote.

Obviously, Brown’s path becomes easier the higher the turnout among African Americans and the more solidly he is able to consolidate their votes. If black turnout inches up to 27% and Brown wins 95% of their votes, he would need just one-third of the non-black vote to win a majority.

Crucial to Brown is not just the racial composition but which non-blacks vote. In particular, reading the tea leaves of the Gonzales poll, whites in Baltimore City and the DC suburbs seem more likely to support Hogan. If they turn out at low rates, it would be easier for Hogan to reach the very high share of the non-black vote he needs. In contrast, Hogan would likely benefit from higher turnout in the Baltimore suburbs, Western Maryland, and the Eastern Shore.

Although Hogan is winning Republicans solidly, independents lopsidedly, and even a chunk of Democrats, his path remains difficult. Here is the share of the white vote won by a series of  Democrats according to exit polls:

Ben Cardin in 2012: 39%
Barack Obama in 2012: 43%
Barack Obama in 2008: 48%
Martin O’Malley in 2006: 45%
Ben Cardin in 2006: 48%
Barbara Mikulski in 2004: 56%
Townsend in 2002: 34% (estimate)

According to the Gonzales exit poll, Hogan leads Brown among whites by 59% to 31%.  If you divvy up the undecided voters in the same proportions as decided voters, then Brown would have 34.4% of the white vote. The last time Democrats scored this low in a statewide election was when Ehrlich beat Townsend in 2002–and blacks will certainly end up a higher share of the electorate than in that year and probably vote at a higher rate for Brown. Moreover, only the Gonzales survey, which was conducted for Republicans shows Brown with this low level of white support.

Lots to watch for tomorrow night. But if Brown gets at least 37% of the white vote, he is almost certain to win. And the share of the white vote he needs will decline if (1) black turnout goes above 25% and (2) the share of blacks who vote for him exceeds 90%. Another sign to watch is changes in turnout in Montgomery relative to the rest of the State. If Montgomery turnout drops relative to other jurisdictions, that could spell trouble for Brown.