You can iterate through each RID and update the to_MEAS field. Ex:
table = "Sample"
ridList = []
with arcpy.da.SearchCursor(table, ["RID"]) as cursor:
for row in cursor:
ridList.append(row[0])
del cursor
ridList = set(ridList)
for RID in ridList:
toMeasList = []
with arcpy.da.SearchCursor(table, ["RID", "to_MEAS"], "RID = '" + RID + "' ") as cursor:
for row in cursor:
toMeasList.append(row[1])
del cursor
toMeasList.sort()
with arcpy.da.UpdateCursor(table, ["to_MEAS"], "RID = '" + RID + "'") as cursor:
for row in cursor:
row[0] = toMeasList[-1]
cursor.updateRow(row)
del cursor
