Well, I do think it's at least somewhat helpful for his cause, partly because it means he dodges a number of potentially bad outcomes and partly because it's a good talking point for him and his campaign that he has been "exonerated". But I'm doubtful it changes things very much because judgments about Trump and his conduct are already so polarized. Folks who think he's a fine fellow victimized by delusional liberals will continue to believe that and foiks who think he's a lying slimeball will continue to think that, even he didn't directly conspire with the Russians. And these views of course are highly partisanized.
In addition, while there are segments of the Democratic party, activist circles and elements of the press who have invested a lot in believing Trump colluded in some way with the Russians, the general run of real world Democratic politics has not been so concerned with this. Nate Silver on 538 points out:
"Somewhat contrary to programming decisions on cable news, the Russia investigation wasn’t a huge point of emphasis for Democrats in the 2018 midterm campaign, nor has it been during the presidential campaign so far."
And Larry Sabato and Kyle Kondik on Crystal Ball say:
"The Democrats did not really run on the Mueller probe in the 2018 campaign, and for the most part, the 2020 candidates haven’t really been doing that either. Now the Democratic contenders will certainly not do so, though other investigations of Trump may bear fruit and become campaign fodder."
These are both very well-reasoned takes and I recommend them.
Without stretching too far, you can even make an argument that this report, by effectively taking Russia collusion off the table, does the Democrats a favor. This way they won't chase the will 'o the wisp of taking Trump down outside of the ballot box, which was highly unlikely to work and might have backfired. Now they have no choice but to beat him the old-fashioned way--by getting more votes in the electoral college. That was the right idea to begin with.