Looking to profit from the projected $6 billion in campaign spending in the 2012 election cycle, Twitter announced that it will start selling political ads in the form of its promoted tweets, accounts and trends, launching today with placement for GOP presidential candidate Mitt Romney.

The pilot group for political advertising consists of five presidential candidates and national political party committees, including Mr. Romney, a Twitter spokesman said. Political ads will be differentiated from Twitter's other promoted products with purple icons instead of the regular orange, and campaigns can enable a Federal Election Commission-compliant notification revealing the ad's backer, viewable when users mouse over the ads.

Political ads will be priced just like the rest of Twitter's promoted product suite, with advertisers paying for keyword-targeted promoted tweets based on user engagement like retweets, replies or click-throughs on a link. Tweets backed by campaigns won't surface in users' timelines, though Twitter last week launched a functionality where promoted tweets from a test group of brands like Pepsi, Disney and American Express can show up in any timeline based on a user's public signals.

In the political ad context, a Twitter user could see a promoted tweet from Mr. Romney's handle (@MittRomney) at the top of their results by doing a search with his name, for example.

Branching out into political ads is an obvious move for Twitter, as having a handle on the platform has become almost automatic for elected officials and candidates. To lead its effort, Twitter announced the hiring of Google veteran Peter Greenberger as political sales director in charge of a Washington-based team he'll be tasked with hiring. Mr. Greenberger built and managed Google's first political sales team in his four years at the company.