Forget for a moment the unwieldy Democratic field and all the talk of different "lanes" to the nomination in Milwaukee. The Democrats have basically two paths to defeating President Trump and making it back to the White House: turn out their voters who stayed home (or voted Green Party) in 2016 or win back the Rust Belt Obama-Trump voters who turned the Electoral College red. To do that, they need to identify a nominee who motivates more voters than he or she scares away.

Unfortunately, that is easier said than done. The remaining Democratic contenders are split between those who are safe with swing voters but might not sufficiently excite the base and those who could get key progressive constituencies to the polls but risk frightening other potentially gettable voters into casting their ballots for Trump.

These camps overlap considerably with establishment versus insurgent, centrist versus left, but not entirely. Former Vice President Joe Biden has (or at least had) substantial African-American support while occupying the center lane. Fellow center-ish former South Bend, Indiana, Mayor Pete Buttigieg so far does not. Similarly, Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren are both progressives. It's a lot easier to see Sanders playing with Midwestern Obama-Trump voters at the same time he turns out progressives than Warren, who has greater appeal to affluent, college-educated suburbanites despite her economic platform.

Sen. Amy Klobuchar occupies the center lane, but it's possible the Minnesotan could also convert some more progressive women, especially in the primaries, if Warren bows out. Former New York City Mayor Michael Bloomberg is a weird grab bag of progressive and centrist positions, combined with lots of money. For the moment, he is polling well with African-American voters in some surveys. But will that hold up under campaign scrutiny? So far he is untested among actual voters. Maybe he would do well against Trump in places like Pennsylvania, Michigan, and Wisconsin, but there are good reasons to suspect he might not.

Buttigieg and Bernie voters seem to very much dislike each other. It's easy to imagine a similar dynamic between Bloomberg, a billionaire, and Sanders, who doesn't believe billionaires should even exist in the first place. Sanders voters may be the most likely to stay home or vote for Trump in the critical states if their man is not nominated, especially if they perceive any establishment hijinks.

Longtime Democratic campaign professionals argue that with Trump looking beatable it's no time to take any major risks. "It's like we're losing our damn minds," said James Carville. Many Beltway Democrats still remember losing to Richard Nixon with George McGovern in a 49-state landslide. But recent elections haven't always been kind to the Democrats' safe candidates, either. Michael Dukakis, John Kerry, and Hillary Clinton all were risk-averse — and they all lost. Walter Mondale was a liberal, but no McGovernite radical. He was defeated in a 49-state landslide too.

In the 2012 Republican primaries, Tea Party Rep. Michele Bachmann confidently expressed that Barack Obama would be a one-term president. The implication was that Obama's re-election prospects were so dicey that even she could beat him. Some Democrats feel the same way about Trump today. But many others don't. And Republicans nominated the safest candidate to run against Obama yet still lost.

There is also the matter of whether they should run against the angry political climate Trump has fostered in this country, winning over voters who are exhausted by the president, or to match Trump's anger. Consider Nancy Pelosi ripping up the State of the Union text or Bloomberg and Trump trash-talking each other on Twitter. Democrats are also divided about whether it's preferable to create a mass movement that shifts the political Overton Window dramatically and permanently to the left, or whether their goal should be just to get rid of Trump now.

The polls don't offer much guidance on how to resolve these tensions. Some national polls, like Quinnipiac, show Trump losing to all top-tier Democratic candidates. Yet some battleground state polls show Trump has maintained his Electoral College edge even against the safer candidates like Biden.

Democrats are going to have to gamble one way or the other. It's just a matter of how much of a risk they are willing to take.

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