You are given two lists of product names:

• catalog_names — the official catalog entries;
• incoming_names — names provided by an external supplier with slight variations.

Your goal is to assign each supplier product name to the closest matching catalog name using the difflib library from the Python standard library.

Follow these steps:

1. For each element of incoming_names, compare it with every element of catalog_names.
2. Use the SequenceMatcher class from the difflib module to calculate similarity scores.
3. For each incoming name, find the catalog entry with the highest similarity score.
4. Store all matches in a dictionary named matched_products, where keys are supplier names and values are the closest catalog names.

Make sure that the variable matched_products is declared and contains the correct matches.