assumer

[Rufus]

Not sure I quite get this:

Pour une partie du "peuple de droite", sensible aux messages de Nicolas Sarkozy, la ligne nationale-conservatrice, malgré l'influence de Patrick Buisson, n'est pas advenue, alors que la référence au gaullisme étant devenue pure incantation, elle était désormais possible. C'est à ce refus d'assumer qu'elle impute sa défaite en 2012.

Translation thus far:

For a part of the "nation of the right", sensitive/receptive to the messages of Nicolas Sarkozy, the national-conservative line, despite the influence of Patrick Buisson, didn’t work, and yet the reference Gaullism having become pure incantation, it would have been possible. It is to this refusal to come together that it attributes its defeat in 2012.

Thank you for any thoughts...

[Vedas]

.

"Assumer" is  come to terms with/ accept the idea

In other words:

The 2012 defeat can be attributed to the refusal of the idea that Gaullism was then a possibility to hold on in the campaign.