and the development of a blue wave suggests that Senate Republicans are likely to become more independent over the next few years. He may have a base, but they know it isn't enough to elect them.
So they need to find a way to reach potential supporters in the burbs. That means redoing the GOP message. Which means moving against Trump on many issues.
They may have a better chance in 2020 if they can get rid of him fairly quickly and install Pence as their guy. He may be an unctuous flatterer, but as far as I know he isn't in Putin's pocket.