One big difference is that outside of states with lots of referendums (referenda?), the target audience is completely different. Lobbyists only need to influen

One big difference is that outside of states with lots of referendums (referenda?), the target audience is completely different. Lobbyists only need to influence the opinions/judgments of a handful of regulators or several dozen legislators. Campaign strategists need to find and target a few million swing voters. Of course, having public opinion on your side can be extremely helpful when influencing legislators, hence the root comment's caveat re: a grassroots campaign.