PARIS — President Emmanuel Macron of France chose a party loyalist Tuesday to head the country’s police and counterterrorism operations, underscoring a focus on personal allegiance among his aides in a government some analysts have called the most top-down in modern French history.

The appointment of Christophe Castaner, who once declared “an aspect of love” in his relationship with Mr. Macron, to lead the Interior Ministry came on a day of government reshuffling in lesser posts. Mr. Macron took on eight new government ministers and got rid of four others, none big names in French politics.

But nothing had fueled as much intense speculation in Parliament and political circles as how the French president would fill the gaping vacancy at the Interior Ministry left by the resignation of his most senior aide, Gérard Collomb, who quit two weeks ago.

Would the new minister, whose offices are just down the street from the president’s in the heart of Paris, breathe fresh life into a government undermined by a sharp drop in public approval? Or would Mr. Macron close ranks and circle the wagons?