Though he's more conservative than my taste, I'm OK with the decent Mr. Painter joining the race with incumbent Tina Smith (Minnesota's former Lt. Governor, appointed to fill the seat after Al Franken's resignation). However, with Minnesota being more of a Blue state than middle-of-the-road, I prefer seeing a Senator there who fits that populace, which Ms. Smith is closer to. What I'm "more OK" with is someone like the moderate Mr. Painter (who as a lifelong Republican probably leans more conservative than liberal) running in states that are more conservative, moving the far right closer to the center, and hope we see that happen.
That aside, having a lifelong Republican like the Bush Ethics Chief running as a Democrat because, when deciding what to do, he didn't "know whether there’s a place for me" in the Republican Party sends a massively loud and booming signal.
No, there is not a place in today's Republican Party for an ethical moderate.