Nonprofit donor management platform EveryAction is buying Mobilize, a company that connects Democratic campaigns to volunteers and helps marshal activists toward progressive causes. Mobilize, formerly known as MobilizeAmerica, grew out of Higher Ground Labs, an incubator focused on leveraging tech for left-leaning political causes and campaigns. With the acquisition, EveryAction can now extend Mobilize’s organizing tools to its existing base of more than 15,000 clients, which includes the Sierra Club and the Human Rights Campaign.