It’s easy to get whiplash looking at the polls. I’ll give you just two examples from today’s menu to demonstrate my point. A new national Fox News survey has excellent news for Joe Biden and plenty of rationale for making him the Democratic Party’s presidential nominee in 2020.

Democratic primary voters increasingly feel the need to nominate a candidate who can beat President Trump in 2020, and more think Joe Biden can do that than any of the other top Democratic hopefuls. In addition, while most Democratic primary voters are satisfied with their field, more than a quarter wish they had other options, according to a new Fox News Poll.

Biden leads the nomination race with the backing of 31 percent of Democratic primary voters, followed by Elizabeth Warren at 21 percent, Bernie Sanders at 19 percent, and Pete Buttigieg at 7 percent. In early October, Biden was at 32 percent, Warren 22, Sanders 17, and Buttigieg 4.

Biden leads Trump 51 percent to 39 percent. That’s the largest margin of any candidate in the poll and makes Biden the only candidate to carry an actual majority of the vote or to hold Trump under 40 percent. Biden also scores highest among Democrats as the candidate who best shares their positions on issues and as the most likely candidate to beat Trump.

But the nomination isn’t won in a national election, and an Iowa survey conducted by New York Times/Siena College Research has very little good news for Biden and plenty of rationale for not making him the party’s nominee in 2020. The top line numbers aren’t disastrous but he does come in fourth place at 17 percent behind Elizabeth Warren (22 percent), Bernie Sanders (19 percent), and Pete Buttigieg (18 percent).

Most striking in the survey, which polled 439 likely Democratic caucus-goers in the last week of October, was that Biden pulled only 2 percent of his support from 18- to 29-year-olds, and only 3 percent from 30- to 44-year-olds. His support came almost exclusively from voters older than 45. (The Iowa poll has a small sample size, though the poll was weighted for age, race, region, turnout, gender, and education.)

This age divide in the Democratic field isn’t only in Iowa, and it isn’t a new phenomenon. It’s reflective of a larger ideological fight that transcends race as a dividing line in the Democratic Party. Younger voters — both white and nonwhite — who are typically more progressive are backing candidates like Warren and Sanders, while older Americans are sticking with Biden.

Of course, you can spin these results two ways. If you want to defend Biden’s candidacy, you can argue that young voters lean so hard against the Republican Party that Democrats don’t really need to worry about persuading them with their candidate. Biden’s strength is that he does about as well as all the others despite getting virtually no first-choice support from anyone under 45 years of age. He’s the best option for digging into Trump’s support.

Yet, it seems pretty dangerous to ignore the near-unanimous consensus of young voters that they do not want Biden as their alternative to Trump. Maybe the vast majority of them will hold their nose and vote for him in the general election, but how many will lose interest and not vote? How many will volunteer or donate money?

There’s no simple answer to these questions.Young people (in this case, people under 45) have more appetite for risk, and Biden represents the opposite of risk. The surest way to lose to Trump is to run a candidate whose policies make people so nervous that Trump looks like a safer bet. Biden isn’t going to create that problem and Trump will have a hell of a time trying to beat that drum. But a return to normalcy sounds better to people who can actually remember an economy that worked for them, and that excludes the youngest voters who came of age near or right after the Great Recession.

Much of Trump’s base has been watching their local economy contract since the 1970’s, and it has made them angry and not a little crazy. Millennial voters are similar in their desire for a change from the status quo, which is why radical change has more appeal to them.

Biden’s advantage is that his appeal is strongest among the swingiest voters. He won’t maximize Democratic turnout, but he will avoid creating weaknesses in the suburbs where older white professionals remember the Obama and Clinton days very fondly because they prospered after difficult times under the Bushes. His appeal to older voters helps reduce the generational gap and presents incredible problems for Trump in his effort to win a narrow majority from a very divided electorate.

He appears safe because he consistently polls the best in head-to-head matchups against Trump, and voters who want a sure thing and aren’t looking for big changes are comfortable with him.

But Biden would have to perform on the campaign trail. A lot of people don’t see a vibrant candidate who is sure on his feet. There are reasons to doubt that he’d be as much of a sure thing as he currently appears to be once the general election kicks off.

There’s probably more risk in going with Biden than is reflected in these survey results. His candidacy could also be a lost opportunity for progressives. After all, he’s not the only one showing a strong lead against Trump. If any of them would win, why play it safe when a more ambitious option is available?

It doesn’t help that some polls show Biden in a commanding position and others show him tanking.

I can’t tell you who to support, but I can say that Biden presents a real conundrum. If he’s your guy, it probably means that you’re not too uncomfortable financially but you’re very uncomfortable culturally. You want Trump out, and anything that risks that outcome isn’t worth considering. That’s a completely valid point of view, especially when you consider that the more progressive candidates aren’t going to be able to enact their bolder proposals anyway. But it is not really clear that Biden is the safest choice. That could be a mirage. And maybe it’s worth rolling the dice and risking a loss rather than getting too little change at a time when everything appears broken.