Mail voting in 2020 US primaries became more common as COVID-19 spread | Pew Research Center
Trump's big advantage: open primaries.
US election 2016: Donald Trump sweeps five US states - BBC News
Maryland Presidential Primaries 2016: latest Democratic polls Apr 2016 | Statista
2016 Republican Party presidential primaries - Wikipedia
2016 Democratic Party presidential primaries - Wikipedia
South flexes its political muscle in 2016 primaries | Facing South
Detailed Maps of Where Trump, Cruz, Clinton and Sanders Have Won - The New York Times
The Modern History of the Republican Presidential Primary, 1976-2012 – Sabato's Crystal Ball
News Coverage of the 2016 Presidential Primaries: Horse Race Reporting Has Consequences | Shorenstein Center
2016 Republican Party presidential primaries - Wikipedia
The Republican debate: meet the 2016 candidates | US elections 2016 | The Guardian
/https://static.texastribune.org/media/images/2016/05/03/Ted_Drops_Out.jpg "Cruz Ending Campaign After Indiana Loss to Trump | The Texas Tribune")
Cruz Ending Campaign After Indiana Loss to Trump | The Texas Tribune
File:U.S. states (and territories) by election methods, 2016 (Democratic Party).svg - Wikimedia Commons
2016 United States presidential election - Wikipedia
Some Democrats voting in GOP primaries to block Trump picks | AP News
A Tale of Two Elections: Clinton's 2016 Primary Performance Versus 2008 – Sabato's Crystal Ball
Storylines to Watch in Tuesday's 2016 Presidential Primaries and Republican Caucuses - ABC News
Super Tuesday: Delegate Tallies From Presidential Primaries And Caucuses - capradio.org
United States Presidential Election of 2016 | History & Facts | Britannica
Turnout in 2016 primaries so far rivals 2008 record | Pew Research Center
United States Presidential Election of 2016 | History & Facts | Britannica
