From Jonathan Bernstein:
In normal times, the events offer a free week of advertising for the parties and their candidates. Will the usual media norms apply during a pandemic?
Conventions for the past 50 years or so have served two big functions. As quadrennial meetings of party actors, they offer the same socializing and networking and identity-building opportunities that any large organization’s convention does. And they advertise the party and its presidential ticket. For the latter, the official podium program is only part of the effort. Media norms dictate in normal cycles that the broadcast networks relocate much of their news and even some of their other personnel to the convention’s host city and devote a week’s worth of coverage to the party. The cable news networks, too, usually make the conventions their dominant story for the week, as do all the online political sites.
This suggests that as long as both the partisan and the neutral political media still treat this year’s conventions as the real thing, they will actually function a lot like normal, even without having all the delegates as a backdrop.
Political advertising isn’t usually very successful at persuading voters to switch their support from one candidate to the other, and that’s not usually the main function of conventions. What conventions can do is trigger weak partisans — those who generally support the party but don’t pay a lot of attention to politics and don’t think of themselves as automatic party voters — by reminding them of their political orientation.