Story highlights
- It is impossible for Sanders to win enough pledged delegates in the remaining contests to become the Democratic nominee
- "I will continue to run an issue-oriented campaign," Sanders said
Washington (CNN)Vermont Sen. Bernie Sanders said Friday he plans to keep fighting for the Democratic nomination all the way to the convention in Philadelphia, but did not slam the door shut on possibly joining Hillary Clinton's ticket.
Asked by CNN's Wolf Blitzer if he would accept a hypothetical offer to be Clinton's running mate, Sanders said he would talk about it with her after the convention.
Photos: Bernie Sanders in the spotlight
U.S. Sen. Bernie Sanders, an independent from Vermont, is the longest-serving independent in the history of Congress.
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Photos: Bernie Sanders in the spotlight
Sanders, right, leads a sit-in organized by the Congress of Racial Equality in 1962. The demonstration was staged to oppose housing segregation at the University of Chicago. It was Chicago's first civil rights sit-in.
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Photos: Bernie Sanders in the spotlight
Sanders takes the oath of office to become the mayor of Burlington, Vermont, in 1981. He ran as an independent and won the race by 10 votes.
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Photos: Bernie Sanders in the spotlight
Sanders, right, tosses a baseball before a minor-league game in Vermont in 1984. U.S. Sen. Patrick Leahy, center, was also on hand.
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Photos: Bernie Sanders in the spotlight
In 1987, Sanders and a group of Vermont musicians recorded a spoken-word folk album. "We Shall Overcome" was first released as a cassette that sold about 600 copies. When Sanders entered the U.S. presidential race in 2015, the album surged in online sales. But at a CNN town hall, Sanders said, "It's the worst album ever recorded."
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Photos: Bernie Sanders in the spotlight
Sanders reads mail at his campaign office in Burlington in 1990. He was running for the U.S. House of Representatives after an unsuccessful bid in 1988.
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Photos: Bernie Sanders in the spotlight
In 1990, Sanders defeated U.S. Rep. Peter Smith in the race for Vermont's lone House seat. He won by 16 percentage points.
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Photos: Bernie Sanders in the spotlight
Sanders sits next to President Bill Clinton in 1993 before the Congressional Progressive Caucus held a meeting at the White House. Sanders co-founded the caucus in 1991 and served as its first chairman.
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Photos: Bernie Sanders in the spotlight
Barack Obama, then a U.S. senator, endorses Sanders' Senate bid at a rally in Burlington in 2006.
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Photos: Bernie Sanders in the spotlight
Sanders takes part in a swearing-in ceremony at the U.S. Capitol in January 2007. He won his Senate seat with 65% of the vote.
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Photos: Bernie Sanders in the spotlight
Sanders chats with Dr. John Matthew, director of The Health Center in Plainfield, Vermont, in May 2007. Sanders was in Plainfield to celebrate a new source of federal funding for The Health Center.
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Photos: Bernie Sanders in the spotlight
Sanders speaks to reporters in 2010 about the Obama administration's push to extend Bush-era tax cuts. Three days later, Sanders held a filibuster against the reinstatement of the tax cuts. His speech, which lasted more than eight hours, was published in book form in 2011. It is called "The Speech: A Historic Filibuster on Corporate Greed and the Decline of Our Middle Class."
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Photos: Bernie Sanders in the spotlight
Sanders and U.S. Rep. Jeff Miller, chairman of the House Committee on Veterans' Affairs, walk to a news conference on Capitol Hill in 2014. Sanders was chairman of the Senate Committee on Veterans' Affairs.
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Photos: Bernie Sanders in the spotlight
In March 2015, Sanders speaks in front of letters and petitions asking Congress to reject proposed cuts to Social Security and Medicare.
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Photos: Bernie Sanders in the spotlight
In July 2015, two months after announcing he would be seeking the Democratic Party's nomination for President, Sanders spoke to nearly 10,000 supporters in Madison, Wisconsin. "Tonight we have made a little bit of history," he said. "You may know that some 25 candidates are running for President of the United States, but tonight we have more people at a meeting for a candidate for President of the United States than any other candidate has."
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Photos: Bernie Sanders in the spotlight
Seconds after Sanders took the stage for a campaign rally in August 2015, a dozen protesters from Seattle's Black Lives Matter chapter jumped barricades and grabbed the microphone from the senator. Holding a banner that said "Smash Racism," two of the protesters -- Marissa Johnson, left, and Mara Jacqueline Willaford -- began to address the crowd.
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Photos: Bernie Sanders in the spotlight
Sanders shakes hands with Hillary Clinton at a Democratic debate in Las Vegas on October 13. The hand shake came after Sanders' take on the Clinton email scandal. "Let me say something that may not be great politics, but the secretary is right -- and that is that the American people are sick and tired of hearing about the damn emails," Sanders said. "Enough of the emails, let's talk about the real issues facing the United States of America."
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Photos: Bernie Sanders in the spotlight
Sanders embraces Remaz Abdelgader, a Muslim student, during an October 2015 event at George Mason University in Fairfax, Virginia. Asked what he would do about Islamophobia in the United States, Sanders said he was determined to fight racism and "build a nation in which we all stand together as one people."
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Photos: Bernie Sanders in the spotlight
Sanders waves while walking in a Veterans Day parade in Lebanon, New Hampshire, in November 2015.
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Photos: Bernie Sanders in the spotlight
Sanders sits with Killer Mike at the Busy Bee Cafe in Atlanta in November 2015. That evening, the rapper and activist introduced Sanders at a campaign event in the city. "I'm talking about a revolutionary," Killer Mike told supporters. "In my heart of hearts, I truly believe that Sen. Bernie Sanders is the right man to lead this country."
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Photos: Bernie Sanders in the spotlight
Comedian Larry David and Sanders appear together on "Saturday Night Live" on February 6. David has taken the role of Sanders in a series of sketches throughout the campaign season.
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Photos: Bernie Sanders in the spotlight
Sanders and his wife, Jane, wave to the crowd during a primary night rally in Concord, New Hampshire, on February 9. Sanders defeated Clinton in the New Hampshire primary with 60% of the vote, becoming the first Jewish candidate to win a presidential primary.
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Photos: Bernie Sanders in the spotlight
Sanders speaks at a campaign rally in Ann Arbor, Michigan, on March 7. Sanders won the state's primary the next day, an upset that delivered a sharp blow to Clinton's hopes of quickly securing the nomination.
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Photos: Bernie Sanders in the spotlight
Sanders speaks at a campaign event in New York's Washington Square Park on April 13.
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Photos: Bernie Sanders in the spotlight
Sanders speaks at a rally in Santa Monica, California, on June 7. He pledged to stay in the Democratic race even though Hillary Clinton secured the delegates she needed to become the presumptive nominee.
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Photos: Bernie Sanders in the spotlight
Sanders endorses Democratic presidential nominee Hillary Clinton at a rally in Portsmouth, New Hampshire, on July 12.
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Photos: Bernie Sanders in the spotlight
Sanders addresses delegates on the first day of the Democratic National Convention in Philadelphia, Pennsylvania, on July 25.
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Photos: Bernie Sanders in the spotlight
Sanders brings a giant printout of one of Donald Trump's tweets, in which the President-elect promised not to cut Social Security, Medicare and Medicaid, to a debate at the Senate in Washington on January 4.
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"Right now, we are focused on the next five weeks of winning the Democratic nomination. If that does not happen, we are going to fight as hard as we can on the floor of the Democratic convention to make sure that we have a progressive platform that the American people will support," Sanders said on "The Situation Room." "Then, after that, certainly Secretary Clinton and I can talk and see where we go from there."
It is impossible for Sanders to win enough pledged delegates in the remaining contests to secure the Democratic nomination, but it remains possible, if unlikely, that Clinton might not win the 2,383 delegates needed for the nomination either, which would set up a potential convention battle in Philadelphia.
"We're going to be in this until the last ballot is cast," Sanders said Friday. Clinton's delegate lead relies in part on the help of more than 500 super delegates -- state party officials and other elected Democrats who can vote for whoever they want -- who support her.
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The Clinton campaign and her supporters have struggled to find a successful strategy for pushing Sanders out of the race. Clinton appeared to be gaining momentum after a series of routs in the northeast, including a blowout victory in New York.
But Sanders won an upset victory over her in Indiana last Tuesday.
Most recently, Clinton told CNN's Anderson Cooper she respects Sanders' decision to finish out the contests.
"I know there are some contests ahead and I respect Sen. Sanders and whatever choices he's making. And I have a lot of empathy about this, Anderson. You know, I ran to the very end in 2008," she said this week.
Asked if he would focus his fire on Donald Trump, with the hopes of helping whoever the Democratic nominee is, Sanders said he would focus on both of them.
"I will continue to run an issue-oriented campaign," Sanders said. "Will I be taking on Donald Trump? Absolutely. Will I be discussing the differences of opinion Secretary Clinton and I have? Yes I will."
Trump tweeted Friday that "Crooked Hillary has ZERO leadership ability. As Bernie Sanders says, she has bad judgement. Constantly playing the women's card - it is sad!"
But Sanders said that was something he never said.
"You read that tweet, that is nothing that I have ever said about Hillary Clinton," he told Blitzer.