A Clinton win would mean the president's policy legacy is kept intact, while a Trump victory would make the election all about a backlash to Obama's tenure.
Days of devastating events rooted in the tension between African-Americans and police prompt political leaders to speak frankly about bigotry and what they think should be done to stop it.
The president made the proposal as part of a comprehensive look at the Affordable Care Act's legacy in an article under his byline in JAMA, the top journal of the American Medical Association.
For purely political trips, a campaign reimburses the government for use of Air Force One. But trips that mix business with campaigning are murkier, rules-wise, and who pays is more opaque.
Hillary Clinton and President Obama both came out swinging against Donald Trump and his response to the attack in Orlando. At times it seemed like they could be reading from the same script.
Clinton said she is looking forward to working with Bernie Sanders "during the campaign and then after the inauguration," as the rivals figure out how to unify.