But Scalia is not the only figure who looms large in this race. Former U.S. presidents, and our current commander in chief, have as well.
Many of the candidates have found themselves continually struggling with the legacy of the past presidents. And one of the challenges that both the Democrats and Republicans face is to figure out how to position themselves in relation to previous inhabitants of the White House.
And since almost all of these presidents are still alive, they continue to make themselves part of the conversation and add a dynamic element to the race that fuels the free-for-all style we have been witnessing.
Each president poses a different kind of challenge.
For Republicans, Ronald Reagan has remained the gold standard for the GOP -- the Republican who was loyal to conservative principles but a politician who also knew how to build a broad coalition and govern. Almost all of the candidates, including Donald Trump, have argued that they can be the next Reagan.
While he offers a powerful symbol for Republicans about how they can be successful as leaders, the contrast between what he did and our current crop of Republicans often produces unfavorable results. Each time a candidate like Trump or Ted Cruz compares himself to Reagan, the public is reminded of how rightward the GOP has drifted and how nasty some of the current campaigns have become.
Shadow of George W. Bush
George W. Bush has been an even bigger presence -- even before he takes to the campaign trail this weekend to support his brother's effort in South Carolina. Jeb Bush has dealt with the problem of his brother from the start. While some Bush nostalgia has set in, it has been pretty limited. Outside of South Carolina, the negatives of his two terms outweigh the positives. Bush 43 has served a similar role for Republicans that Jimmy Carter (who also came up in the debate when Senator Marco Rubio invoked his name in an unfavorable way) has for Democrats -- an example to the opposition of what could go wrong with their party in the White House.
As predicted, Jeb has struggled to get out of his brother's shadow and he has often had problems defending the family name. Unable to separate himself from George W. Bush's unpopular war in Iraq, there have been questions about what the continuation of this dynasty would be. The legacy of Iraq has hampered efforts by some Republicans like Marco Rubio or Lindsey Graham to revitalize a hawkish foreign policy agenda. They talk about America being tough, but many Americans remember what that can mean under a Republican
When Republicans attack Obama for the growth of ISIS, they have had to find ways to minimize the role of the Iraq war in helping to create the tensions there. At the same time, Rand Paul had trouble making a case that libertarian conservatism could really exist in the wake of a two-term Republican president who vastly expanded the power of the national security state.
Notably, Bush has also been a factor in the Democratic race. In response to Hillary Clinton's claims of foreign policy experience, Bernie Sanders has fought back by citing her vote in favor of Bush's unpopular war. She says she has experience and wisdom, Sanders has reminded voters of her connection to the unpopular president to undercut her judgment.
Presidents Richard Nixon and Gerald Ford also made an unexpected appearance in the Democratic debate, when Sanders criticized Hillary Clinton for speaking so highly of their top national security adviser, Henry Kissinger whose record has led some liberals to consider him a war criminal
. The charges stem from Kissinger's role in supporting brutal regimes that served U.S. interests and conducting covert policies without congressional consent.
Bill Clinton factor
Sometimes it feels like Bill Clinton is running for re-election, given how present he is. For Hillary Clinton, he has been a huge factor in shaping perceptions about her, often unfairly. One of the major attacks leveled by Sanders is as much about Bill Clinton as it is about her.
Sanders is rejecting the centrist brand of Democratic politics that Bill Clinton promoted, as well as the deregulation of Wall Street that his administration pushed in the 1990s and which were directly connected to the 2008 financial meltdown.
Hillary Clinton also has struggled because of the fears that exist about whether her presidency would produce another period of scandal warfare like as in the 1990s. Trump also brought up Bill Clinton to question his wife's commitment to fighting for women's causes given his checkered personal record and how his White House aggressively attacked the character and reputations of the women who accused him of misconduct.
At the most practical level, Hillary has had to deal with the benefits and problems of Bill's role on the campaign trail, since the connection is so intimate.
Clinton can be one of the toughest partisan campaigners around and he has already hit Sanders pretty hard. If Hillary Clinton wins the nomination, he will be a force for the Republicans to reckon with.
Bill is a reminder of the kind of partisan fighter the Clintons can be. On the other hand, as she learned in 2008, he needs to be controlled, as some of his statements could become a problem. When Clinton blasted Sanders right before some of the New Hampshire primary, saying that "when you're making a revolution you can't be too careful with the facts," some Democrats recalled when his attacks on Barack Obama in South Carolina caused a backlash against Hillary.
During an otherwise lethargic performance in the most recent debate, Bernie Sanders came to life when asked to name an influential leader. He cited Franklin Roosevelt, since it was FDR who redefined the role of government.
President Obama: Is he on the ballot?
And then there is President Obama. As the current inhabitant of the White House, everyone has to deal with him. Democrats have been struggling to figure out how to position themselves on his presidency.
Hillary Clinton has decided that her best bet is to connect herself directly to his administration, praising the President repeatedly while arguing that she will take Obama's accomplishments even further. She has become increasingly strident in connecting her own candidacy to the legacy of the administration. On foreign policy, this connection has been more challenging given the problems that the U.S. faces overseas and the controversy over Obama's record.
Sanders, on the other hand, has had more trouble. He has tried to take the position that he agrees with much of what the administration has done, though he makes clear he wishes Obama had done more to keep working with the grass-roots operation he mobilized in 2008 and he stands for stronger forms of government. How much this will hurt Sanders, particularly with the African-American vote in South Carolina, will soon become clear.
For Republicans, it's as if Obama is on the ticket. Most of their attacks are about what this administration has done on every front and the name of the game has been to connect the Democrats to the President, and to distinguish themselves from him.
Every time that Obama has taken action in recent months, such as on gun control, he has only become a bigger part of their campaign narrative. The fact that his approval ratings remain below 50% have become an opening for them to attack, even though the economy has recovered substantially from the 2008 crash.
Obsessing over past presidents and what they did may obscure that the challenges of 2016 aren't those of the 1970s, 1990s or early 2000s. But even though we are electing our future leaders, the past remains very much an issue on the hustings.
Sanders and Trump have benefited from their ability to separate themselves from the problems that some of their party's presidents can bring, though, as we have seen in the past, sometimes the ex-presidents can become powerful allies on the campaign trail and symbols of what a successor could accomplish.