Campaigning is talking to the public. Lobbying (or "Government Affairs") is talking to policymakers. They have some commutative components and they often work in conjunction with each other at some level, but they are entirely different professions/practices.

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.

Plouffe ran an exceptional 'outsider' campaign, where a lot of the party apparatchiks were already pledged to Clinton, and the Obama campaign built their own outside infrastructure to compete.

Lobbying is about 'insiders'. You can nudge them with popular pressure, of course, but it's not like an election where the party insider only has 1 vote they completely control at the end of the day.

They are very similar. Similar players in both worlds. Slightly different skills - but mostly the same basic work. just different constituents.