Well, a few things.
1) The trendline was toward Manchin in the final week of 2010, it is against him in the final week of 2018.
2) Raese was a toxic candidate, far worse than Morrisey.
3) Raese didn't have WV's God Emperor enthusiastically supporting and holding rallies for him.
And most importantly:
4) 2010 was before a majority of West Virginia voters began to see all Democrats as irredeemable members of an anti-white hate group. The line of demarcation for this shifting of the paradigm was on November 7th, 2012. One day after Manchin was last on the ballot!
Morrisey is not a good candidate, lol. Let's look at some other differences.
1. 2010 was a GOP wave year.
2. The Democrats just elected a governor in 2016, he overpeformed Clinton by over 40 points as well. It doesn't matter if he is a republican now, he RAN as a democrat.
3. In 2010, there were some public polls that showed Manchin losing in the last month or so. The only poll we've seen with Manchin behind in this State in the past several months is......NRSC.
I didn't say Morrisey was a good candidate (in fact I think he's garbage), just that he's better than Raese. It's not hard to be better than Raese. 
Anyway, there will be no Dem wave in WV, so the political climate doesn't mean much. Justice won because he was/is a Republican. In fact, the (D) next to his name weighed him down so much that he couldn't even get a majority of the vote despite fitting WV like a glove. All because he was (falsely) affiliated with the anti-white hate group.
Maybe Manchin can eke out a plurality win because enough of the voters who refuse to vote for the anti-white hate group vote third party/skip the race/do a write-in because they also find Morrisey abhorrent, but he's by no means safe.
You seem to be very pessimistic about Manchin's chances. Polls have consistently shown him to be the safest Romney-state Democrat throughout the year. Moreover, some recent polls showed him clearing the 50% mark. I wouldn't be too surprised if Morrisey ends up doing better than has been previously predicted, but I do not think that he will win at this point. Now, if Evan Jenkins had won the Republican nomination, I think Manchin would be on track to lose like Heitkamp.
West Virginia is still a State where we could have an upset. Reminds me of the Warner/Gillespie Race a bit. Trump wouldn't have gone to WV today if this weren't close.
Poll
