Former Vice President Joe Biden is currently leading the early Democratic primary polls, partially thanks to his perceived strength against President Donald Trump.

Biden is largely succeeding because other candidates are not perceived to be nearly as electable as he. But once other candidates become more viable, their success could threaten his unique appeal.

The sometimes gaffe-prone Biden has been able to maintain his perception of electability largely by staying out of the public eye and campaigning less than other candidates.

On the debate stage, Biden is likely to face direct confrontation from progressive candidates like Sens. Bernie Sanders and Elizabeth Warren, who have been openly criticizing Biden on the trail.

A poor debate showing could contribute to fewer voters feeling confident of Biden's ability to take on Trump on the national stage.

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Former Vice President Joe Biden is currently leading the early Democratic primary polls partially thanks to his perceived strength against President Donald Trump — but the first primary debates later this month will put his biggest asset to the test.

While the elusive concept of "electability" can be influenced by a number of factors including a candidate's race and gender, we attempted to break down who Democratic voters see as the most likely to beat Trump

To determine exactly how likely Democratic voters perceive each candidate's chances of beating or losing to Trump, INSIDER has been conducting a recurring SurveyMonkey Audience national poll. You can download every single poll here, down to the individual respondent data.

Read more about how the INSIDER 2020 Democratic primary tracker works.

In INSIDER polling — specifically, looking at the data from the six polls conducted since April — Biden not only has very high name recognition but very high levels of approval among the Democratic electorate.

Out of the 83% of self-identified Democrats who are familiar with Biden, 60% would be satisfied with him as the Democratic nominee compared to 20% who would be actively un-satisfied, the best performance for any of the candidates in the field, plausibly because they also perceive Sanders to be electable, too.

Biden is also the only candidate for whom more than half of the respondents believe can win against Trump, with 73% of voters believing he would beat Trump compared to 16% who think he would lose in the May 17 edition of INSIDER's recurring poll.

While political pundits often tout Biden's appeal to working-class whites and organized labor, he also dominates among African-American Democratic primary voters. In a late April CNN poll, for example, 50% of nonwhite respondents preferred Biden as the nominee compared with 14% who preferred Sanders, and 47% of black women supported Biden in a Morning Consult's surveys.

Biden is largely succeeding because other candidates are not perceived to be nearly as electable as he. But once other candidates become more viable, their success could threaten his unique appeal.

Read more: Joe Biden just delivered a show of force in a key early voting state

Take Vermont Senator Bernie Sanders, for example. While Biden and Sanders may seem to represent completely opposite wings on the Democratic primary, 45% of Biden supporters would also be satisfied with Sanders as the nominee.

In INSIDER polling, 47% of self-identified Democrats believed Sanders would beat Trump compared to 30% who think he would lose, the second-best result in the field behind Biden.

Sen. Kamala Harris of California comes in third place, with 35% of voters believing she would beat Trump compared to 33% who think she would lose, a relatively steep drop-off from Biden's numbers despite Harris' strong performance in the field.

Biden's primary asset is his perceived electability and wide appeal to a number to different demographic groups. And his entrance into the race in late April failed to change that perception, or substantially impact the polling numbers or perceived electability of the rest of the 2020 field.

The sometimes gaffe-prone Biden has able to maintain the veneer of electability largely by staying out of the public eye and avoiding situations where he could put his foot in his mouth, instead of trying to out-campaign the rest of the field.

Already, candidates in the progressive wing of the field such as Sanders and Sen. Elizabeth Warren have lodged some thinly-veiled attacks at Biden over his moderate policy positions, and his notable absence from the California Democratic Party Convention, which he skipped to campaign for LGBT rights in Ohio.

The debates could present Biden, who served in public office and public life since 1970, with a chance to solidify his status as the most experienced candidate in the field and the most prepared to take on Trump.

Read more: Some Democrats are already blasting Joe Biden's reported 'middle ground' climate change plan for not going far enough

But if he ends up on the same stage as Sanders or Warren, he's at risk of being stridently attacked as out-of-touch with today's Democratic primary and today's America, and not providing a sufficient rebuttal to their criticisms.

If progressive candidates succeed in making Biden look weak on stage compared to the rest of the Democratic field, it could contribute to making fewer voters confident of his ability to take on Trump on the national stage.

Biden has successfully held onto his status as the frontrunner since joining the race, but if he has a poor showing on the debate stage, he could be just a few gaffes away from his support and his perceived electability fleeing fast.

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