Go to Dave Leip’s Atlas of US Presidential Elections for good charts on the primary votes so far. One interesting data point: Though Barack Obama is now considered a slight underdog in the Democratic race and John McCain is considered the near-certain Republican nominee, so far Obama has received a bigger share of Democratic primary votes (42%) than the share McCain is getting of Republican primary votes (37%). The difference is the winner-take-all primaries on the Republican side, which have allowed McCain to get all the delegates from states like Florida where he hasn’t won the popular vote by all that much. 

As of this writing (with almost all the votes from yesterday tabulated), Obama has received 6.5 million primary votes to McCain’s 4.2 million votes. Hillary Clinton tops them both with 7.6 million votes.