There is proof, people have had their likes and retweets removed from the presidential candidates x account on multiple cases.

Also, most of the accounts tweets only have around 200k impressions, which is much lower than what the old x account(which was banned by the government) used to get.

Also another point, erdogans government is so intolerant of seeing the presidential candidate is that they've literally took down banners and posters that mention anything about him. It is "illegal" to have a banner ad that has the text "Ekrem İmamoğlu" or a photo showing İmamoğlu. Do you really think a government that goes to such extremes won't try and persuade Twitter to shadowban the presidential candidate's x account?