The key here is that Trump is now a Republican president. That requires the former TV star to rise above the political fray and put the party’s interests first by advancing a message of optimism and unity. That message is as important in defeat as in victory. Instead, Trump’s tweet sold Gillespie down the river by suggesting that the GOP candidate was a failure from the start. Aside from being unnecessary, it makes Trump appear arrogant and rude.
Moreover, it’s also counter-productive for Trump’s own interests in that it will likely isolate those Republicans who remain unsure of him. They’ll look at Trump’s tweet and think, “the guy doesn’t care about the party, he only cares about himself.” And regardless of whether that assessment is accurate or not, fueling GOP dissatisfaction is not going to help Trump to unify Republicans around his legislative agenda.