What think tanks are associated with Macron's En Marche and pan-European Renaissance? What newspapers (possibly French) are read by the voters/supporters of En Marche and Renaissance?
About think tanks, the question is easy:
The Institut Montaigne: Laurent Bigorgne the director of the Institut was a supporter of EM
The Gracques which actively supported EM.
These two organisations represented the right-side of the "parti socialiste": We can say they are liberals (In France liberals are considered as rightist (or at least "centristes")).
Source (in french, and not free): https://www.monde-diplomatique.fr/2019/12/RZEPSKI/61104 Still in french https://fr.wikipedia.org/wiki/Laurent_Bigorgne
About newspapers which support Macron: I'm not an expert, but L'Express seems fit (The chief editor of this newspaper did a rap for Macron: https://www.ladepeche.fr/article/2017/08/17/2629395-christophe-barbier-cree-malaise-imaginant-macron-train-rapper.html https://rmc.bfmtv.com/emission/christophe-barbier-je-ne-suis-pas-macroniste-c-est-eventuellement-macron-qui-est-barbier-iste-1655526.html )
There are probably other candidates (le nouvel observateur, more anecdotally le 1), but it's less obvious
It's much harder to answer what is read by a Macron voter because his electorate has changed a lot since his election, but (personal point of view) I would say at the beginning Lemonde which was full of sympathy for him, and then, I don't know, I'm not even sure his voters read newspapers...