The Federalist (by Jordan Gehrke) now has a story online that lays out the background of how McConnell blew it in Alabama
"Mitch McConnell Is The Reason Doug Jones Is A Senator"
"While Mitch McConnell and his allies will try to blame conservatives for nominating Roy Moore, it’s important to remember that McConnell is the main reason Roy Moore was nominated.
The moment it was clear there would be a Special Election to replace Jeff Sessions, McConnell and his PAC, Senate Leadership Fund (SLF) declared they would back Luther Strange and vowed to spend millions on his behalf.
Strange was a flawed candidate from the jump. The circumstances around his appointment by scandal-ridden Governor Robert Bentley were sketchy at best, and rightly or wrongly, voters just never trusted him.
Looking back, an establishment candidate like Strange, beset by issues surrounding his appointment was never going to win a runoff in an anti-establishment state like Alabama–certainly not in the year after Donald Trump was elected.
Judge Roy Moore soon entered the race, followed by Mo Brooks, a conservative congressman from northern Alabama with a very solid voting record. A member of the House Freedom Caucus in the mold of Jeff Sessions, Brooks resonated with conservative grassroots. As I have outlined before, my firm was retained by Brooks and helped a pro-Moore superPAC in the runoff against Strange. (We did no work for Moore in the General Election.)
Determined to keep a Freedom Caucus member out of the Senate, McConnell and SLF swung into action with a little over a month to go, spending over four million dollars carpet-bombing Mo Brooks. They told everyone who would listen that they were going to destroy Brooks. They even hired consultants for a potential primary challenger in his house seat, just to intimidate him.
Why did they do all this?
Because they decided early that it would be easy to beat Roy Moore in a runoff. Unfortunately for them, Alabama voters didn’t really like the meddling by DC. This, coupled with the fact that Strange was so unpopular, meant that despite the attacks on Brooks, the race was tied in the closing days of the campaign with Brooks surging....."
-- more at the link --
http://thefederalist.com/2017/12/12/mitch-mcconnell-is-the-reason-doug-jones-is-a-senator/