...as he looks to maintain his tight grip on the GOP base.
The behind the scenes is building his influence in local and state republican committees, etc. which is a lot of work and depends on people showing up at local city/county republican meetings and voting for local party positions, etc etc etc. These rallies can help facilitate that cause. I assume his grip on these folks is not as great as the base as a whole, but he should be stronger than he was a few years ago even though he "lost" the election. So I think the statement is fair and accurate.
I recognize you may have a completely different interpretation.