In the run-up to Hillary Clinton's speech on Trump and his endorsements from white nationalists (specifically naming the Alt-Right) and conspiracy theorists, I was contacted by two different journalists from The Guardian (see here and here), by apparent coincidence. You can follow those links to see some of the remarks I provided. I have a few additional thoughts about that speech:
1) It is pretty clear to me that Clinton was sending a message to a segment of Republican and Republican-leaning voters. Why else would she have said kind things about Dole, Bush, and Ryan? I doubt the Clinton camp is worried about shoring up its support among minorities, given Trump's terrible numbers among non-whites. However, there are plenty of respectable, suburbanite Republicans who would be appalled to be affiliated with a racist movement. They certainly would not want to have anything to do with anything as low-brow as the KKK (not the KKK actually exists as a real organization anymore, but that's a separate discussion).
2) In my view, the large amount of time focused on Alex Jones was a mistake, as it added a layer of complexity to what is already a confused subject. The attempt to link Trump to 9-11 Truthers fell flat. Most people don't know who Alex Jones is. Those who do, and aren't already fans, probably view him as a mostly-harmless (and possibly entertaining) kook. It may have been unwise for Trump to go on his show, but it probably didn't change anyone's opinion on Trump.
3) The attacks on Alex Jones and the Trump movement for embracing "dark conspiracy theories" would have been more credible in my view if she had not offered a conspiracy theory of her own. The link between Putin and the Alt-Right is pretty weak -- which is not to say that many Alt-Righters do not love Putin. I cringed at her statement: "And the grand godfather of this global brand of extreme nationalism is Russian President Vladimir Putin." Perhaps this was a smart political move (I doubt it was), but I did not find it a convincing argument.
4) Whether or not discussing the Alt-Right was a shrewd political move for this election is not clear to me, but this was probably a victory for the Alt-Right regardless of what happens in November. If you read what the Alt-Right has been saying on Twitter and elsewhere, they clearly view this as a sign that they have entered the mainstream debate. They can no longer just be ignored as annoying trolls after the Democratic nominee named them in a major speech.
5) This relates to points 4, and 1, but the degree to which the speech was both effective for this election and helps the Alt-Right depends on how polarizing Clinton remains as a political figure. That is, if Clinton really is as hated among the Republican rank and file as talk radio presumes, then simply being hated by Clinton may raise a movement's esteem among a large segment of the electorate. That is, there may be some people who had never heard of the Alt-Right, and if they found it on their own would hate it, but because Clinton views it as threat, they may be willing to give it a second hearing. I'm not sure yet how likely that is.
6) That said, some of Alt-Right's excitement over this is probably unwarranted. Yes, as a result of this speech, lots of people started googling "Alt-Right." How many of these people subsequently found the major Alt-Right websites, bothered to read them in any detail, and then decided that the Alt-Right is onto something? I suspect the number is more than zero, but I doubt the numbers are particularly high.
So in conclusion, I don't think this speech really changed very much. This was a big moment for the Alt-Right, but the movement's baseline of support was pretty small to begin with. It could double in size and still be a marginal movement. I also doubt the speech will change anything fundamental about the campaign; the poll numbers have not moved much over the last few days.