I'll try to come up with something different than the cliched "Democrats are simply more open-minded and reasonable (and even lovably gullible in pursuit of their noble causes!) than their barbaric Republican counterparts."
Many of the least popular Republican governors on that list seem to be either 1) from states that are not ancestrally Republican but only drifted toward the GOP for
cultural reasons (which tend to often attain a more national spotlight than a local one) AND/OR 2) from states that are known as having more ... err ... "rabid" GOP electorates that would hold these politicians to more extreme stances and make them feel as if they needed to take bolder actions - the same types of actions that make the national GOP unpopular.
Conversely, the six most popular Republican governors seem to be from states that either 1) have relatively moderate Republican electorates that simply want a
little bit of change from the very liberal status quo (e.g., Massachusetts and Maryland) or 2) have residents that are quite happy with the way things are going in their states and don't have a real desire to "shake things up" (e.g., Wyoming and Texas). Both of these situations are conservatives' bread and butter, and conservative politicians can become quite popular under these circumstances, as they can be responsible and govern in a way they know is best. I would argue that there is decent evidence of responsibly "conservative" governing working quite well.
Ironically, many of these "RINO" governors can campaign in a much more "conservative" spirit than their national GOP counterparts, who constantly have to take the traditional rhetorical space of traditional "liberals" and make bold promises to millions of voters, put forth bold new ideas that distinguish themselves from the status quo, excite voters with bombastic assertions of how unfair things are, etc. When Republicans are forced to do this, they back themselves into a corner where they either have to 1) take things way too far and overstep even their own ideological beliefs to appease a rabid base and purity-minded voters (e.g., excessive tax cuts that don't make economic sense) or 2) be forced to backtrack on campaign promises and "betray" their supporters in favor of acting responsibly (e.g., Bush 41 choosing to raise taxes after "Read My Lips!").
I maintain that the "natural habitat" of a successful conservative politician is when liberals are getting their way. It is very easy for someone like Larry Hogan to come into a high tax/high unemployment/high cost situation, suggest to voters that "enough is enough," implement a small change or two (even if it's "all he can get away with" in that state) and remain incredibly popular as a responsible reformer. I would argue no national Republican has successfully achieved something in this "conservative" of a manner since perhaps even Eisenhower. When people can see the effect that a responsible conservative can have - anywhere from Wyoming to Massachusetts - rather than what they have come to expect from the national GOP, it resonates with them. For all of the talk about who is a "true conservative" and who is a "RINO," someone like Larry Hogan is quite literally a conservative hero, haha.
