at this stage, it's a republican talking point that kirk's shooter's motives were political and partisan. [View all]
it's not unreasonable to guess that the killing of a prominent politically divisive figure might be political, but at this stage that's merely one of several possibilities.
without a suspect in custody, without a manifesto, without really anything to go on other than who the victim was, we really don't know.
famous people get death threats all the time, and sometimes there are actual attempts, and sometimes these attempt result in a death. so it's entirely plausible that this was just a killer seeking notoriety by killing someone famous. nothing to do with politics in particular, just that fact that kirk was famous, which some sick people figure will give themselves a moment in the spotlight.
it's also entirely possible that the killer knew something we don't know about kirk. many killings involve a personal connection, and just because someone is famous doesn't mean they're immune from that. business disputes or infidelities or other personal grievances can result in violence and even death.
we may well find out that the motives were political. in fact, i'm willing to guess that this is the leading theory. but that's only speculation at this stage, and republicans are milking it by flooding the zone with accusations against their usual targets.
if it turns out that kirk had an affair and an angry spouse did him in, it would theoretically ruin all republican attacks on democrats in this matter, but the damage will have already been done, many people cling to the first theory they hear about, contrary to all later evidence, especially if it confirms their worldview.
never mind that even if it was politically motivated, there's still plenty of room for it being done by a right-wing extremist who thinks kirk wasn't fascist enough or didn't support donnie enough.