Original sentence: The Huffington Post is an American news website, content aggregator, and blog founded by Arianna Huffington, Kenneth Lerer, Andrew Breitbart, and Jonah Peretti, featuring columnists and various news sources
Edited sentence: The Huffington Post is a liberal or leftist American news website, content aggregator, and blog—founded as an alternative to existing conservative online media outlets such as the Drudge Report—by Arianna Huffington, Kenneth Lerer, the late Andrew Breitbart, and Jonah Peretti, featuring various leftist columnists and various news sources