I think Madrid will aim to wrap up the league title sooner to pay more attention to the UCL.So they will try to beat Barca today no matter what, because if they win today their Laliga Title is secure. On the other hand, Barca will try to keep their season alive by defeating Real Madrid so it will be a different battle in a different mindset.
Real Madrid will not allow its closest rivals to win at home to Real Madrid today, because it is not just about the title this season. But it is also about the prestige of a team like Real Madrid, which would be quite embarrassed if they were defeated by their closest rivals at home in today's match. So it will be quite possible for Real Madrid to play as well as possible today in order to win at home and this will also make it easier for Real Madrid to win the La Liga trophy this season.
The El classico use to be one of the most watched football in the world. Real Madrid will give all to make sure they defend their home against their eternal rival. They just got a good result from the champions league, so they are still in a good mood, so I expect they to use this their good mood and trash Barcelona. Madrid are very comfortable in the league as things stands now, even if they lose it won't worry them that much, but if they lost it will be very disappointing to them. Though Madrid might be playing with caution here so that their best players don't pick up injuries as they are still looking ahead to play in the Champions league. This might have a little to play in this game, but I expect Ancelotti to field a strong team to battle Barcelona.