Donald Trump is running for president. Many believed or hoped that the Donald's latest foray into national politics was nothing more than a public-relations move, not a serious attempt to reside at 1600 Pennsylvania Avenue. But now that Trump holds the lead in national polls, as well as polls in Iowa and New Hampshire, it's time to take his campaign seriously. Media outlets like Huffington Post and the Wall Street Journal, which are covering Trump's run as an entertainment story, not a news story, are making a mistake. If Trump wants to be a serious candidate for president, and...