I haven't yet. Did Evans think McCarthy erred with Marshall?
As I recall, yes. Evans wrote that McCarthy made several mistakes, mostly form and style, rather than substance.
The actual sequence is quite revealing. The Dems put Marshall in at state in part to have an unassailable war hero figure there. Marshall then went up to the hill and testified that there were no problems, it had all been cleaned up long ago - without getting into names or cases. The committee taught him otherwise afterward, giving him specific FBI info on security risks still in important positions. Marshall gets right on it and uses authority congress gave the Truman administration years before - but that they hadn't used - to rapidly can several of these security risks.
Well, then the left press screamed about the injustice to their fine upstanding Ivy friends. And Marshall backed off, just like that. He had tried to do the right thing as a matter of course, but he was the sainted George Marshall and he got good press, not bad press. He didn't take this gig to ruin his reputation but to burnish it. That ended that.
Marshall didn't have an unpatriotic bone in his body, and Evans goes into detail refuting McCarthy on him and his decisions. He correctly finds the source of bad policies Marshall signed off on in Asia, in the advice he was getting from the Acheson crew, which was effectively running state day to day, below Marshall's figurehead-marquee level.
Acheson does not get off so easily. In Evans portrayal, he clearly connived to keep reds in the department because it was his and the Dems turf and reserved for his high brow buddies, and those uncouth ruffians in congress didn't have any business sticking their noses in. Truman and his justice went along with that out of pure partisanship and to avoid political blame, in public - Evans has the internal memos of liberal senate types warning Truman that McCarthy was scoring heavily and they had to do something, etc.
The commie networks themselves were playing the rest of the left like a fiddle, getting them to defend the worst cases to avoid admitting they'd been in bed together for so long already etc.
But it didn't actually work, and McCarthy won outright, as long as it was just him against the left. He didn't lose until he kept doing in despite the fact the it was now Ike in the whitehouse. He wanted serious action, Ike wanted it as just a good past campaign issue that would now go away to avoid embarassment. It was their collision on that, that ruined McCarthy. Ike had it in for him over Marshall, there is no question - Ike concluded from that episode that McCarthy was reckless and unfair etc.
Point being, it took the center right to break him, the left alone did not manage it.