AP:

It can be hard to see where Donald Trump the business ends and Donald Trump the presidential candidate begins.

When Trump is confronted by his political rivals, the Republican front-runner’s company attorney threatens lawsuits on corporate letterhead.

When Trump’s campaign needs event space, private businesses sometimes provide it free.

The political novice’s use of corporate resources — his own and others — is just one more campaign tool. But it has drawn the attention of federal regulators, as well as campaign-law experts who say some of what he’s doing could be illegal.