Bernie Sanders marked the one-year anniversary of his campaign for the White House on Sunday by promising a “contested” Democratic convention this summer. The Vermont senator continues to argue that he could still win the Democratic nomination, despite his opponent, Hillary Clinton’s, lead in pledged delegates and superdelegates.

In a bold move, Sanders said today that he vowed the Democratic Party’s convention would be “contested” unless Clinton won enough pledged delegates to win the nomination without superdelegates. Sanders has essentially vowed to fight Clinton for the support of the superdelegates before they formally vote at the convention in July.

“It is virtually impossible for Secretary Clinton to reach the majority of convention delegates by June 14 — that is the last day that a primary will be held — with pledged delegates alone…. She will need superdelegates to take her over the top at the convention in Philadelphia,” Sanders told members of the press at the National Press Club in Washington, according to the Huffington Post.

“In other words,” he added, “the convention will be a contested contest.”

Bernie Sanders says it's not impossible to topple Hillary Clinton in the Democratic race https://t.co/oLNo53N8Wr pic.twitter.com/D6mygjYDnP — CNN Politics (@CNNPolitics) May 1, 2016

Superdelegates are Democratic Party leaders and elected officials who are not bound to any candidate and are free to vote for whomever they want at the convention. Their coveted votes could decide the nomination between Clinton and Sanders (currently 520 back Clinton, compared to 39 for Sanders). They have almost universally supported Clinton’s bid for the presidency, but the votes aren’t final until July, and Sanders has made it clear he plans to try to convince the superdelegates to switch to him.

Bloomberg Politics monitored the delegate count in the Democratic primary so far.

“The Bloomberg Politics delegate tracker shows Clinton with 2,156 delegates, including 520 super delegates, while Sanders has 1,357 delegates, 39 of whom are super delegates. A candidate needs 2,383 delegates to clinch.”

ABC News also noted that despite Clinton’s lead, the support of the superdelegates has now become decisive in the nomination process.

“While it is unlikely that either candidate will be able to win enough pledged delegates alone to secure the nomination, according to estimates from ABC News, Clinton has the backing of 520 super delegates at this point, bringing her very close to the threshold.”

Sanders Gets A Million Donations In April While Bankers Bern Up The Phones – 2.4 Million... https://t.co/1Fg65KqobF pic.twitter.com/TelGCA16PS — Inquisitr News (@theinquisitr) May 2, 2016

The Sanders campaign staff has been arguing for a contested convention for months, but this was the boldest statement made about the strategy going forward. Sanders called on superdelegates in states such as Washington state and Minnesota, where he won contests by landslide margins, to switch their allegiance, saying their votes should reflect the will of the people.

“If I win a state with 70 percent of the votes you know what, I think I’m entitled to those super delegates,” he said, according to HuffPo. “I think the superdelegates should reflect what the people in the state want. And that’s true for Hillary Clinton as well. I can’t tell you one thing for me and another thing for Hillary Clinton.”

Sanders’ case for the nomination and the Democratic elites’ support also rests on proving he will be the strongest candidate against Donald Trump should he become the GOP nominee. Sanders argues that he is the best person for the job, as reported in Bloomberg.

“The evidence is extremely clear that I would be the stronger candidate to defeat Trump or any other Republican,” Sanders said of the Republican front-runner, citing several nationwide polls showing him doing better than Clinton in a general election against the billionaire real estate magnate.

“We intend to fight for every vote in front of us and for every delegate remaining,” he added, according to ABC.

The candidates will once again face off in the Indiana primary on Tuesday.

[Photo by Win McNamee/Getty Images]