Imagine your perfect car: comfortable seats, room for your whole family, great gas mileage, quick acceleration and performance brakes. Best of all, it’s within your budget and currently on the market—as long as you buy it soon. But instead of signing the papers, you allow a friend to convince you to hold out for a fancy prototype model that remains unavailable to regular consumers. Suddenly, the first car is off the market and you’re stuck driving the old junker you hate.

For voters who want a progressive alternative to Hillary Clinton, Bernie Sanders is the best car on the market. Senator Elizabeth Warren — a charismatic populist with national name-recognition and an impressive donor base — would make a phenomenal candidate, but she’s rejected the possibility every chance she gets. The quicker her fans stop waiting in vain, the better chance Sanders will have to fight for the values voters associate with Warren.

Progressives have spent several years dreading an uncontested primary season dominated by Hillary Clinton, who has made little effort to conceal her closeness to Wall Street or her hawkish record of supporting the Iraq War and the Patriot Act (twice). After the 2014 elections, progressive nonprofits Democracy for America (DFA) and MoveOn asked their members which candidate they would support in the 2016 primary. With over 164,000 votes cast, 42 percent of DFA members (including me) supported Elizabeth Warren. Bernie Sanders came in second with 24 percent, with Hillary Clinton right behind him at 23 percent. A Warren candidacy was possible then, but now that she’s demurred, Sanders is the obvious choice to inherit Warren’s base.

However, Sanders has only a short window of time to win over these Warren holdouts, who could provide him with the poll numbers and donations he needs to have a fighting chance in the early primaries. DFA and MoveOn – who have collectively raised $1.25 million for their Run Warren Run campaign — mean well, but are doing more harm than good by doubling down on their determination to draft Warren.

In a phone interview, Democracy for America executive director Charles Chamberlain argued that Warren might still enter. “Look at Bill Clinton, he didn’t announce he was running until October,” Chamberlain told me. “We’re building this race to make it possible for her to get in as late as she needs.” He’s is right that Bill Clinton didn’t officially announce his campaign until October 3, 1991. But unlike Warren, Clinton had never decisively ruled out running. He had announced his presidential exploratory committee in August, and according to Clinton insider David Brock, had been “seriously considering” a presidential run ever since late spring of 1991. As a two-term governor and former state attorney general, Clinton was also highly experienced in campaigning. He didn’t need any persuasion from advocacy groups to enter the race.

By contrast, it took months of intense public pressure for Warren to enter her first political campaign, against Massachusetts Senator Scott Brown. And as soon as the presidential buzz started in December of 2013, Warren did her best to stifle that conversation by pledging to serve the length of her term, which ends in 2019. She’s gone on record six times saying she’s not running for president in 2016. Referencing MoveOn’s persistent efforts to draft Warren, Late Night host Seth Meyers recently joked, “If you asked a girl to prom this many times without a yes, they would ask you to transfer schools.”