LOVELAND – What should have been a rallying cry for U.S. Sen. Michael Bennet as he prepares for a tough election in November was hijacked by thousands of Bernie Sanders supporters angry that the Democratic Party superdelegate is supporting Hillary Clinton despite Sanders’ clear victory in Colorado.

“Change your vote. Change your vote,” the crowd chanted as Bennet took the stage Saturday at the Budweiser Event Center in Loveland. Sanders’ supporters didn’t stop yelling when Bennet started and then interrupted his speech several times.

Sanders, a U.S. senator from Vermont, officially won 41 of the 66 delegates up for grabs in Colorado. Clinton only won 25 but probably also will pick up most if not all of the 12 superdelegates in Colorado, who can vote for whomever they choose at the Democratic National Convention in Philadelphia this summer.

Matthew Flaherty, who lives on the U.S. Air Force Academy with his father who is retired from the military, walked around the convention holding a Bernie sign attached to a large stick. He ran as a delegate hoping to go to Philadelphia at the 5th Congressional District Assembly Friday night.

Flaherty said he was among those chanting at Bennet.

“Just a little bit,” he said. “I wasn’t as loud as the people in front of me.”

Flaherty said he’s not voting for Bennet unless the former head of Denver Public Schools considers changing his vote as a delegate and also if he changes his stance on hydraulic fracturing, often known as fracking.

But Democrats don’t have an alternative in the race. Bennet didn’t pick up a primary opponent and the race is a battleground for control of the Senate. Democrats held both Senate seats in 2014, but Sen. Cory Gardner, a Republican from Yuma, defeated incumbent Mark Udall in a bitter battle that attracted millions of dollars from outside the state.

Bennet is considered similarly vulnerable in a state dominated by independent voters, but Republicans have had a hard time drafting a big name or someone with the star power of Gardner. Five Republicans are still in the race and could drag each other through the mud before a victor is named in the June primary.

“This seat in Colorado could determine control of the United States Senate, which could determine not just one but three Supreme Court justices,” Bennet said. “It could determine who has the ability to make their own health-care decisions, who has the freedom to marry, how we fund our elections and even who has the right to vote. These are significant choices and the stakes are sky-high in 2016, because we are at a crossroads here.”

Pam Hyde, 64 of Henderson, said Bennet hasn’t earned her vote yet and she’s not afraid to write someone in on Election Day. She was among those stomping and chanting at Bennet.

“Wasn’t that great?” she said, wearing a bright yellow cellophane homemade Bernie Sanders hat.

“We need to get rid of the superdelegates,” Hyde said. “They don’t get a free pass if they are not responsive to the population.”

Hyde said she considered being polite during Bennet’s speech, but ultimately decided it was more important to let the politicians know how unhappy she is with the system. Hyde said she is returning to the party after an absence because Sanders motivated her.

Both Sanders and Clinton campaigned in Colorado ahead of the caucuses on March 1 where straw polls were held to allocate supporters to the county and state assembly. A straw poll was held Saturday to determine the final allocation of at-large delegates: 1,915 voted for Sanders and 1,129 voted for Clinton.

Republicans had their assembly in Colorado Springs on Saturday, and Ted Cruz swept every delegate up for grabs and El Paso County Commissioner Darryl Glenn knocked nine other U.S. Senate candidates off the ballot. He’ll face four other candidates who are petitioning on.