Did you miss this sentence in the article?
"There were just enough of these willfully “blind” “single issue purity” voters to hand the Democrats 16 of their 36 victories; this figure being derived from the fact that for the want of just 63,000 more votes spread across these races,.."
OTOH, as we all know here at FR, historically, the mid-term election of a President in his second term has been a big loser. Last year we had a perfect storm of
(1) A President who is argeably, the worst communicator of the television age,
(2) A populace, femenized for the last 30 years, is war weary
(3) A Republican controlled Congress which did little to earn the votes of Republicans. Other than they aren't democrats.
Hence, loser...
It isn't an "article." It's a vanity, written for the sole purpose of trashing conservatives.
Item #3 on your list is probably the biggest of them all. In national politics, it is usually much easier for the opposition party to generate a high level of enthusiasm than for the ruling party. This is mainly because the opposition often does not have to be very specific about where it stands -- it just has to have enough targets from the ruling party (in the form of policy matters) to hold up as incorrect, destructive, and even downright absurd (witness the GOP campaign in 1993-94).