I'm eyeballing the D results with 99% reporting and I think there will be about 520,000 Ds who voted in SC. There were about 440,000 Rs voting in SC. Both were competitive races. The Rs actually had 4 (or 5 if you include Paul) people contesting the race to the 3 that Ds had. Republicans need to start paying attention to the fact that in swing states (IA, NH) Ds are getting twice as many voters. And in red states, Ds are getting 50% more. There is a huge enthusiasm gap and it should be worrying to anyone who cares about Democrats controlling all three elected branches.
[UPDATE] I changed the numbers closer to the actual final numbers.