WASHINGTON - It's hard to see where Donald Trump the business ends and Donald Trump the presidential candidate begins.

The Republican front-runner has made more use of corporate resources than previous candidates.

That has federal regulators asking questions. And campaign finance experts say some of what he's doing could be illegal.

The Trump campaign has answered a federal regulator's demand for the names of his company employees who are doing work for his presidential bid.

One person not on that list is the Trump Organization's general counsel, Alan Garten. The corporate attorney has written letters threatening legal action to those who have been attacking Trump in political advertisements.

A lawyer supporting a rival candidate has filed a complaint with the Federal Election Commission, alleging that is an inappropriate use of corporate resources.