In 2002, when neither Democrat Kathleen Kennedy Townsend nor Republican Bob Ehrlich faced serious primary threats Townsend received roughly 400,000 votes to Ehrlich's 200,000 - a 2 to 1 margin that closely matched the Democrats' registration advantage. Roughly 100,000 Democrats opted to vote against Townsend in the primary. So there was a 2.5 to 1 turnout advantage among Democrats, but 20% lodged a protest vote against Townsend and she went on to lose the general election.
In 2006, neither Ehrlich or Democratic challenger Martin O'Malley faced any primary challenge. O'Malley received 500,000 votes to Ehrlich's 200,000 - essentially the same 2.5 to 1 turnout in 2002, but the Democratic vote was unified.
In 2010, O'Malley faced no serious challenge and Ehrlich did. So far, there have been 411,000 Democratic votes cast and 255,000 Republican votes. Ehrlich has claimed 76% or 195,000. O'Malley has received 86% or 354,000. Three things stands out - 1) Democratic turnout is barely 1.6 to 1 over Republican, an incredibly low ratio, 2) O'Malley's advantage over Ehrlich is thus less than Townsend's over Ehrlich in 2002, and 3) 14% of Democratic voters have lodged a protest vote against O'Malley.
If these ratios hold then tonight will be a bad night for Martin O'Malley and perhaps indicative of a rough general election to come.
In the 5th Congressional District, Majority Leader Steny Hoyer's district, Republicans have nominated newcomer Charles Lollar. In 2008 there were 110,000 Democratic votes cast in the primary and only 28,000 Republican votes - 3.5 to one in a district that is 2 to 1 Democrat. Hoyer won in 2008 75% to 25%. Tonight, there have been 53,000 Democratic votes so far to 25,000 Republican votes - about 2 to 1. This suggests that even Hoyer may have a race on his hands - though odds are still very much in his favor.