While I don't see Gillespie winning I doubt today's indictments will end up having a major factor on the race. For one they don't really show anything that people don't really know about #russiagate (I suspect most people have already made up their minds on the investigation and nothing short of a smoking gun is going to change peoples minds and no today's developments do not constitute a smoking gun.) Secondly in a week this will be old news and likely not have as much of an impact on the race (for individuals that this is a big deal for are probably voting Northam anyway. Most of those voters are strongly partisan dems. ). Thirdly today's news will probably not do a lot to hurt the reputation of the Republican party as a whole as the individuals indicted were either fairly obscure or completely unrelated to the current goverment and #Russiagate. I also take exception to the notion that Governors races are low profile; millions are still spend on advertising as well as loads of local TV coverage of the election to the point that I would expect by now most voters have at least some idea of what they think of both candidates. I also doubt that Republicans are honestly going to stay home just because Manfort was indicted. That is not to say I don't expect that Northam isn't going to win but don't just expect a major over performance of the polls; of course Republicans shouldn't count on the revere from happening either.
I wasn't trying to suggest that the Governors race is low-profile. I was just saying that people's views dominate choices in partisan races the lower you go downballot. There are even studies for this. When people don't know who the candidates are, or don't know what they've been up to, they let their default opinions guide them, and those are pretty much what they think of the president these days.
As for the Russiagate stuff, I disagree with a few of your points, for instance, I think actual indictments like this represents a new step and there are still plenty of soft supporters out there who might be more malleable now that the investigation is more than just leaks on various things, BUT there is also no real way to argue for or against the idea that it will depress turnout, except to pay attention to Trump's approval ratings. If they see a sustained drop that is not within his normal polling numbers, then it is probably having a negative effect. That and maybe having some relevant exit poll questions on election day.
What I meant by high profile race is that voters are more likely to be accustom to the candidates and have an increased chance at viewing the candidates as separate from their parties. Most voters whom are voting based largely on partisan affiliation would have mostly voted that way regardless of conditions simply because they are loyal to their party.
I don't really think today's indictments are really that significant to that many voters because they are figures that are largely figures unknown to voters (I doubt that many voters even remember who Manafort is and voters simply aren't going to change their opinion on the investigation absent a smoking gun.) While I respect the point about the indictment those individuals are fairly obscure to most voters and the charges are not things that have voters link the charges to Trump.