(CNN) With Hillary Clinton's decisive victories in four of the five primary states Tuesday, the math almost certainly won't work for Bernie Sanders. With the results of the most recent primaries, the time has come for Sanders to start winding down his campaign and thinking about what role he can play in the Democratic battle for the White House.

Even though he won't win the nomination, the Sanders campaign has the potential to change the Democratic Party. He will join a long list of failed presidential candidates whose campaigns had a transformative effect on ideas and strategy. A few examples:

--In 1928, New York Gov. Al Smith, who lost in the general election to Herbert Hoover, brought urban Americans into a coalition with the South that would become the center of Franklin Roosevelt's New Deal.

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--In 1964, Arizona Sen. Barry Goldwater ran an insurgent campaign arguing that the GOP had to embrace conservatism. Goldwater's conservative vision was decisively rejected when the nation voted for LBJ in a landslide victory. His ideas, however, would reshape the party.

Photos: Who's running for president? Ted Cruz, Donald Trump, John Kasich, Hillary Clinton and Bernie Sanders, Hide Caption 1 of 6 Photos: Who's running for president?



"So, ladies and gentlemen, I am officially running for president of the United States, and we are going to make our country great again," Trump told the crowd at his announcement. Businessman Donald Trump announced June 16 at his Trump Tower in New York City that he is seeking the Republican presidential nomination. This ends more than two decades of flirting with the idea of running for the White House."So, ladies and gentlemen, I am officially running for president of the United States, and we are going to make our country great again," Trump told the crowd at his announcement. Hide Caption 2 of 6 Photos: Who's running for president?



"These are all of our stories," Cruz told the audience at Liberty University in Virginia. "These are who we are as Americans. And yet for so many Americans, the promise of America seems more and more distant." Sen. Ted Cruz of Texas has made a name for himself in the Senate, solidifying his brand as a conservative firebrand willing to take on the GOP's establishment. He announced he was seeking the Republican presidential nomination in a speech on March 23."These are all of our stories," Cruz told the audience at Liberty University in Virginia. "These are who we are as Americans. And yet for so many Americans, the promise of America seems more and more distant." Hide Caption 3 of 6 Photos: Who's running for president? Ohio Gov. John Kasich joined the Republican field July 21 as he formally announced his White House bid.



"I am here to ask you for your prayers, for your support ... because I have decided to run for president of the United States," Kasich told his kickoff rally at the Ohio State University. Hide Caption 4 of 6 Photos: Who's running for president?



"Everyday Americans need a champion, and I want to be that champion -- so you can do more than just get by -- you can get ahead. And stay ahead," she said in her announcement video. "Because when families are strong, America is strong. So I'm hitting the road to earn your vote, because it's your time. And I hope you'll join me on this journey." Hillary Clinton launched her presidential bid on April 12 through a video message on social media. The former first lady, senator and secretary of state is considered the front-runner among possible Democratic candidates."Everyday Americans need a champion, and I want to be that champion -- so you can do more than just get by -- you can get ahead. And stay ahead," she said in her announcement video. "Because when families are strong, America is strong. So I'm hitting the road to earn your vote, because it's your time. And I hope you'll join me on this journey." Hide Caption 5 of 6 Photos: Who's running for president?



"This great nation and its government belong to all of the people and not to a handful of billionaires, their super PACs and their lobbyists," Sanders said at a rally in Vermont on May 26. Sen. Bernie Sanders , an independent from Vermont who caucuses with Democrats, announced his run in an email to supporters on April 30. He has said the United States needs a "political revolution" of working-class Americans to take back control of the government from billionaires."This great nation and its government belong to all of the people and not to a handful of billionaires, their super PACs and their lobbyists," Sanders said at a rally in Vermont on May 26. Hide Caption 6 of 6

--But Ronald Reagan, who lost in the primaries to President Ford in 1976, brought Goldwater's ideas back into the mix during the primaries and attracted new voters throughout the sunbelt with his right-wing message. He lost in 1976, but his message became the key to his huge electoral success in 1980 and 1984.

--Sen. George McGovern suffered a devastating defeat to Richard Nixon in 1972, but he attracted a coalition of younger voters, African-Americans, anti-war activists and women, who would remain central to the Democratic electorate.

--And when Vermont Gov. Howard Dean ran in 2004 against John Kerry, he offered a strong critique of Bush's intervention, introduced new campaign techniques to reach younger voters, establishing the model, and an agenda that shaped Barack Obama's campaign in 2008.

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Sanders will have this same effect. His campaign won't be forgotten. The most important contribution comes back to his central issue: the role of big money in politics. The Sanders campaign has demonstrated how small donations can be sufficient to fuel a presidential campaign.

A break with orthodoxy

This development comes at a time when most leading campaign finance reformers have been shifting focus from imposing tighter restrictions on large donations to instead creating incentives for candidates to rely on small donations. Sanders has put forth a small donation model that can become the basis for future campaigns, making the Democratic Party less dependent on large donors.

Sanders has also broken with the neoliberal policy orthodoxy that has dominated Democratic politics since the late 1970s, when Jimmy Carter and later Bill Clinton pushed the party toward the center on domestic and foreign policy. Both presidents argued that for Democrats to survive in an increasingly conservative era they would need to shed their attachment to the New Deal and Great Society traditions. They backed a more muscular approach to using military force as a way to push back against Republican claims that their party was weak on defense.

Sanders has rejected this outlook about public policy. On domestic policy, he has emphasized the need to use the government to combat inequality and poverty. He has blasted the orthodoxy of free trade. In both areas, he has influenced Hillary Clinton's policy agenda. And while Democrats have shied away from defending the value of government, Sanders has offered a strong defense of what Washington can do.

The same is true on foreign policy, in an era when Democrats have been reluctant to challenge the hawkish agenda that Republicans have promoted since Reagan. During the Democratic candidates' recent debate in Brooklyn, he strongly criticized Israel for its policies in Gaza, which he called disproportionate to the threat that the nation faced, and he called on policymakers to acknowledge the rights and struggles of the Palestinians.

Redirecting the future

By taking all of these stands he has opened the door for future candidates to do the same. The best tribute to his immediate impact on the policy agenda has been that Clinton has absorbed many of his ideas into her own campaign.

The final, enduring legacy of this campaign will be to reconnect Democratic politicians with grass-roots movements. During the heyday of liberalism between the 1930s and 1960s, political leaders understood that grass-roots movements could be an engine for political success. President Franklin Roosevelt tied his fortunes to the burgeoning union movement and that became the basis of his electoral victory.

LBJ likewise harnessed the energy of the civil rights movement to push back against the conservative forces in the country that were behind Goldwater's election, and to help him build a massive legislative record that he called the Great Society.

Reviving the power of the grassroots

But for many years Democratic presidential candidates have kept grass-roots movements at arms length. Ever since the late 1960s when the anti-war movement turned against LBJ, the grass roots have been associated with the leftward politics that would be unhelpful to winning.

Sanders took a different approach. He has harnessed the immense grass-roots energy that has formed in recent years with movements like Occupy Wall Street. Various unions have also been an essential part of the Sanders mobilization, after many decades when they have felt like second-class citizens in a party that they helped to build. Indeed, his entire campaign has been constructed around a bottom-up, movement-based model.

His campaign has excited Americans between the age of 18 to 29 about the possibilities of politics; they find themselves in agreement with many of his core messages.

So even if this is the end of the Sanders campaign, the impact of what he has done will continue to be seen for years to come. The campaign tactics, the policy issues and the connections between campaigns and the grass roots will never be the same again.

This is why it is particularly important for Sanders and Clinton to form a coalition rather than descend into more bitter division. Doing so will not only create a stronger Democratic ticket against the Republicans in fall, but improves the chances that the party as whole will appreciate what his campaign has offered as a path forward.

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In her victory speech Tuesday evening, Clinton said, "I applaud Senator Sanders and his millions of supporters for challenging us to get unaccountable money out of our politics and giving greater emphasis to closing the gap of inequality. And I know, together, we will get that done."

If Sanders and Clinton can bring a harmonious end to their competition, the party can unite against the Republicans and also absorb the many tactics and ideas that Sanders brought to the table.