Obama outspends Romney on online ads - CNNPolitics
Breakdown: How Campaigns Spend Their Millions - ABC News
U.S. elections 2012 - Obama campaign spending 2011, by category | Statista
A Promised Land: Obama, Barack
How Much It Costs to Run for President? A 40-Year Timeline
How the Trump Campaign Is Drawing Obama Out of Retirement - The New York Times
Obama, campaigning in Georgia, warns of threats to democracy | AP News
How the Presidential Candidates Use the Web and Social Media | Pew Research Center
Obama's Spending: 'Inferno' or Not? - FactCheck.org
Barack Obama 2008 presidential campaign - Wikipedia
PolitiFact | Barack Obama's top 25 campaign promises: How'd he do?
How much money is behind each campaign? - Washington Post
How the Presidential Candidates Use the Web and Social Media | Pew Research Center
INFOGRAPHIC: Obama, Romney Final Ad Spend
U.S. elections 2012 - Obama campaign spending March 2012 | Statista
Obama, Romney both topped $1B - POLITICO
Obama outspends Romney on online ads - CNNPolitics
Obama campaigns for Warnock, Abrams in push for Georgia to vote for Democrats : NPR
How much time is Obama spending on his reelection campaign? - The Washington Post
The 2012 Election: Our Price Tag (Finally) for the Whole Ball of Wax • OpenSecrets
Getting and spending: US election money wars – Channel 4 News
The Internet's Role in Campaign 2008 | Pew Research Center
Illuminating 2020 Report: The 2020 General Election Campaign Advertising on Facebook – Illuminating
The Crazy Cost of Becoming President, From Lincoln to Obama – Mother Jones
R.I.P. positive ads in 2012 election - POLITICO
