Former Vice President Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE said Sunday he would contest the presidential primary nomination at the Democratic convention if Sen. Bernie Sanders Bernie SandersSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Schumer, Sanders call for Senate panel to address election security MORE (I-Vt.) is leading in delegates without securing a majority.

“The rules have been set,” Biden said on CNN’s “State of the Union.”

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Biden questioned Sanders’ take that the candidate with a plurality of pledged delegates the convention should become the nominee.

“I wonder where that view was when he was challenging Hillary when she went in with a commanding lead,” Biden added. “You don't change the rules in the middle of the game.”

Sanders is the only candidate in the field this year to insist that the candidate with the most pledged delegates should be the party nominee. He held the opposing view in 2016 when facing former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Virginia Democrat blasts Trump's 'appalling' remark about COVID-19 deaths in 'blue states' The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE.

Biden’s commitment to challenge the nomination comes after he won his first primary in South Carolina on Saturday.

Biden is trailing Sanders in the number of pledged delegates as the candidates head into Super Tuesday, when the largest number of states will hold primaries and caucuses including Texas and California.