Hillary Clinton and Sen. Bernie Sanders (I-Vt.) speak during the Democratic presidential debate at the Gaillard Center last month in Charleston, S.C. (Mic Smith/Associated Press)

Over the last week, I learned that supporters of Sen. Bernie Sanders (I-Vt.) will melt the pixels on your computer screen if you criticize him, don't sufficiently #feelthebern or say something favorable about Hillary Clinton. Meanwhile, backers of the former secretary of state and 2008 presidential candidate are no slouches in smacking down her detractors, especially those consumed by the Bern they feel. And then there are theprotectors of the legacy of President Obama who aren't happywith the daylight Sanders is putting between himself and the man he hopes to succeed. It's enough to make you think that one side will stay home in November if the other side wins the nomination. And if that happens, Democrats would have themselves to blame for the Republican president unleashed on the nation.

This isn't hyperbole. Look at what happened in 2010 and 2014. Democrats lost both houses of Congress because their voters didn't show up at the polls. Both votes were comedowns from the highs that put Obama in the White House. His election in 2008 as the nation's first black chief executive and reelection in 2012 brought so many African Americans to the polls that theysurpassed the rate of whites for the first time in history.

Why they stayed home in those off-year elections is explained in"Brown Is the New White: How the demographic revolution has created a new American majority" by Steve Phillips. The senior fellow at the Center for American Progress and co-founder of PowerPAC.org makes the case in two stark charts using data from the Office of the Clerk of the U.S. House of Representatives.


(Courtesy of Steve Phillips)

Off-year elections always see a drop-off in voter participation for both Democrats and Republicans. But what happened in 2010 was stunning. "The Democratic drop-off was almost twice as bad as usual," writes Phillips, "and the Republican turnout was almost twice as good as usual." Between the historic election of 2008 and 2010, Democrats saw a plummet of 26 million voters, from 65 million people to 39 million people. Meanwhile, Republicans saw a drop-off of just 7 million voters, from 52 million to 45 million. The GOP took over the House.   


(Courtesy of Steve Phillips)

Six million fewer Republicans voted for Senate candidates in 2014 than in 2008. But 14 million fewer Democrats went to the polls. That 42 percent drop in turnout allowed the GOP to take over the Senate. The 2014 election also saw the Republican majority increase in the House to its largest since World War II.

"Democrats did not lose the House in 2010 and the Senate in 2014 because working-class Whites fled the Party [for the GOP]," Phillips explains. "They lost because voters of color and their progressive White allies stayed home."

[One of the big reasons Clinton and Sanders talk the way they do]

Phillips delivers this data in a chapter titled "Requiem for the White swing voter," in which he argues that Democratic campaigns and candidates should shift their focus from trying to win over the ever-elusive white swing voter to what he calls the "New American Majority." That is, a 51 percent coalition of all eligible voters in the United States that includes 23 percent of progressive people of color and 28 percent of progressive whites. The elections of 2010 and 2014 show what happens when Democrats don't give the majority a reason to vote. Phillips argues that timidity and bungling on the Affordable Care Act and immigration reform served to dampen their enthusiasm.  

brown is the new white_cover.indd(The New Press)

That shouldn't happen this time around. Clinton, Sanders and former Maryland governor Martin O'Malley are all speaking about the issues and policies this majority cares about. Income inequality, immigration reform and the disparate treatment of African Americans on a host of issues, from Ferguson to Flint, have been discussed and debated by the three throughout this campaign. This isn't just a matter of political necessity. Anyone watching them knows what they bring to that discussion is rooted in conviction. 

But the mutual bitterness that emerged in the final days leading up to the Iowa caucuses must not blind Democrats to their need to vote no matter who their nominee is in November. As Phillips writes, Democrats won't hold the White House without "securing the support of 81 percent of people of color and 39 percent of Whites." A repeat of the low turnout from 2010 and 2014 will guarantee a Republican White House and an unraveling of the Obama legacy. No Democrat should want that on his or her conscience.

Follow Jonathan on Twitter: @Capehartj

Jonathan Capehart is a member of the Post editorial board and writes about politics and social issues for the PostPartisan blog.