Sen. Bernie SandersBernie SandersObama book excerpt: 'Hard to deny my overconfidence' during early health care discussions Americans have a choice: Socialized medicine or health care freedom Ocasio-Cortez says Democrats must focus on winning White House for Biden MORE (I-Vt.) won't rule out a presidential bid if no other liberal candidate steps up to run — but suggested Sen. Elizabeth WarrenElizabeth WarrenAll fracked up: Biden's Keystone State breakdown What do Google, banks and chicken salad have in common? Final debate: War Admiral vs. Seabiscuit MORE (D-Mass.) could fit the bill.

Sanders tells the Burlington Free Press that he'd prefer not to run, but if no one else steps up to challenge the "establishment politicians" in 2016, he may feel compelled to.

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"We need a sense of urgency and I don't see that in establishment politicians and I don't see that in the establishment media," he says. "There are people in this world who, ever since they were 12 years of age, they decided they wanted to be president of the United States. That is honestly not me. ... Anyone who really, really wants to be president is slightly crazy because this is an unbelievably difficult job given the crises that this country faces today."

He indicated Sen. Elizabeth Warren (D-Mass.) might earn his backing if she were to run, however.

"I like Elizabeth Warren very much," he said. "Her beauty is that she is very smart. She speaks English. She can explain economics in a way that everybody can understand."

Sanders has previously said he hasn't ruled out a run but put the odds of that happening at 1 percent.

Sanders said if he did run for president he would "probably" run as an independent rather than a Democrat.