Joe Biden hasn’t even announced if he will run for the 2020 Democratic nomination, but that hasn’t stopped Iowans from putting him at the top of their list in a new poll.

A survey conducted by CNN, the Des Moines Register and Mediacom Iowa found that 27 percent of likely Iowan Democratic caucus participants polled, put the former vice president as their first choice, giving him the highest net favorability among possible contenders, with 81 percent. Vermont Sen. Bernie Sanders came in second with 25 percent of those polled saying they would vote for him as their first choice.

In a distant third: uncertainty. A tenth of voters said they weren’t sure who their first choice was 20 months out from the 2020 presidential election — a higher share than those who supported another well-known senator. Massachusetts Sen. Elizabeth Warren trailed in fourth with 9 percent of likely Democratic caucus-goers saying she was their choice for nominee.

A comparison to the December 2018 poll from the trio shows the gap constricting between President Barack Obama’s vice president and the 77-year-old senator. Then, Biden claimed 32 percent and Sanders 19 percent of first-choice votes only three months earlier when neither — along with most other potential candidates — had declared their candidacy.

Democrats, especially moderates — in Iowa and elsewhere — are grappling with how progressive they want their 2020 candidate to be

Though Sanders gained the support of a quarter of the likely Democratic caucus-goers who responded, nearly double that many thought Sanders was too liberal — even as many of the participants in the poll supported progressive issues like Medicare-for-all, a $15 minimum wage, and tuition-free college.

That epitomizes what Sam Rosenfeld described for Vox as the growing rift in the Democratic Party. The party is moving left (in keeping with its long tradition of internal left-liberal activism), while progressive lawmakers reject the idea that they’ve been molded from the traditional Democratic liberalism:

“We have seen insurgent victories in primaries by progressives and also successful campaigns by establishment-backed moderates. All the while, the substance of the party’s agenda continues to move leftward, with both left and centrist candidates standing behind Medicare-for-all, a $15 minimum wage, and tuition-free college.” ...This is good news for the left, and history helps account for what we’re seeing. Sanders supporters and other like-minded progressives, many of them comfortable with the language of socialism and a hard-edged critique of American liberalism, typically portray themselves as a both a new and fundamentally external force in Democratic politics.

And Biden, for all his early popularity, could pose some of the same concerns for the party as Hillary Clinton did in 2016, as Vox’s Matthew Yglesias noted. The 77-year-old is a mainstream Democrat, just “like other mainstream Democrats. But what it means to be a mainstream Democrat has changed significantly since Biden entered the Senate 46 years ago.”

More important, Yglesias added, that decades-long political career could open Biden up to attacks from the right as well, just as Hillary Clinton’s years in the public eye gave her then-opponent Donald Trump a treasure trove of fodder.

What brought Clinton down was public exposure not to her personality — which was sparkling enough to make her the most admired woman in America for 17 years straight before losing the claim to Michelle Obama in 2018 — but extended public scrutiny of every detail of a decades-long career in public life. This, in turn, is the exact same problem Biden will inevitably face as a presidential candidate. Americans like outsiders and fresh faces, not veteran insiders who bear the scars of every political controversy of the past two generations.

Whether the (hugely important) voters in Iowa and those around the country want a veteran lawmaker, self-identifying progressive, or new face, they will have plenty of options. As more and more Democrats enter the race, another recent poll from NBC News and the Wall Street Journal showed even though Trump has strong party loyalty, 48 percent of those polled said they would vote for a Democrat, compared to 41 percent who said they would vote for Trump. It’s going to be a long, uphill battle on both sides of the aisle toward November 2020.