Claude Rains did not receive an Oscar nomination for portraying Paul Ward in White Banners.
The film is technically positioned around the various influence of the somewhat mysterious housekeeper Hannah (Fay Bainter), who in particular endeavors to help the family patriarch/teacher/inventor Paul Ward by Claude Rains. Rains is firmly in non-villainous mode here, which he can ease into as easily as when playing a fiend. Rains making for a rather charming lead to be expected with his refined manner that feels just right for this certain type of intellectual. As usual Rains goes further though than is quite required by the role as he has a bit of fun with the idea of the professor as being slightly a bit eccentric within his inventions. Rains doesn't overplay this but rather brings this certain flourishes, particularly charming flourishes, of a bit of a cheeky style. This nicely grants a bit more towards the character who overall is what one can refer to as a "great guy", who just wants to help those around him for the most part while also making his inventions. The "worst" thing about the man is that he is slightly frustrated that no one takes his inventions seriously, although Rains even portrays this as the man taking it all with rather good humor suggesting that perhaps he doesn't even take it as seriously as he could.
The main thrust of the story then is essentially the housekeeper Hannah pushing those in and around the household to be their best selves including encouraging Mr. Ward's inventions. This leads only a pretty minor arc to work with for Rains as he goes from a quietly passionate charming generous man, to a more openly passionate charming generous man. Rains does this well to be sure but there isn't too much asked of him other than to be his charming self. Now that is sort of more than enough for Rains to make an impact as Rains is rather delightful in these sort of roles bringing such a joyous energy that he works so naturally within his usual refined manner. The only hiccup within the arc is when his protege inventor Peter (Jackie Cooper) lies to him and gives up the secrets to their inventions which other steal. Rains even portrays his moment of anger as wholly reasonable and within character for Ward. Rains is actually particularly good since he conveys the anger of such a man so well by creating as this very internalized direct intensity for the moment that is very reserved fitting for a man who tries never to be angry. This is quickly fixed though leaving only Ward to take over Hannah's role by encouraging her back in the end, and this Rains excels with since he already stood as such a warm figure from the outset. In the pantheon of Rains's performances this is not an overly notable one, but it is a good one to be sure, as to be expected.