Being the opposition party in the era of President Trump raises some new questions for Democrats about what standards they should hold themselves to. A question topping that list, and recently dogging former vice president Joe Biden, is: How much should their own truthfulness matter as they try to defeat someone who is serially dishonest?

Biden has been embellishing and falsifying a story he’s been telling for years about traveling to Afghanistan and pinning a Silver Star on a Navy captain. He never did such a thing, write The Washington Post’s Matt Viser and Greg Jaffe in a deeply reported story last week. It appears he conflated at least three different events.

So what? Biden said in response. “The details are irrelevant in terms of decision-making,” Biden told NPR and Iowa Public Radio over the weekend while campaigning in Iowa. His point was that voters need to judge him on whether he can make big decisions, and you do that by getting at a presidential candidate’s heart. His intentions in telling the story, he said, were good, and his command of its details had no bearing on whether he would be a good president.

“That has nothing to do with judgment of whether or not you send troops to war, the judgment of whether you bring someone home, the judgment of whether you decide on a health-care policy,” Biden said in the interview.

Politics and honesty don’t always go together. But Biden’s mistelling of a story he often repeats is a bigger story than it might have been in other years. That’s because any deviation from the truth among a presidential candidate arguably carries more weight than normal in the era of Trump.

The current president has made more than 12,000 false or misleading claims, according to The Washington Post Fact Checker database. His untruthfulness is a major part of who he is, so it stands to reason his opponents want to draw a contrast by being honest with voters. To that end: Do voters give Biden a pass on his own factual inaccuracies? Or do Democratic voters, increasingly focused on electability, become concerned Biden won’t have the moral authority to take on a central feature of Trump?

These are questions that don’t have answers yet. Biden is arguing that his untruthfulness is not a defining part of how he leads. But is that enough of a contrast for today’s Democratic voters, a majority of whom feel so strongly that Trump needs to go that they want to impeach the president?

Biden has also framed his entire campaign around beating Trump, from his very first campaign announcement. “If we give Donald Trump eight years in the White House, he will forever and fundamentally alter the character of this nation — who we are. And I cannot stand by and watch that happen,” he said.

Biden recently said that he might not be running for president were it not for Trump. “I hadn’t planned on running again,” he told reporters this weekend.

There are lots of ways for 2020 candidates to draw contrasts with Trump. Policy is a big one, of course. But more than any other modern president, who Trump is as a person is just as big a story. He has tweeted racist things about Democratic members of Congress and entire cities. He has been accused of sexual misconduct by more than a dozen women. He’s on film bragging about groping women. He revels in divisiveness.

Democrats are running for president without a road map about how to beat the most nontraditional president in modern memory. Will that create a political market for complete truthfulness? Democratic voters have to decide.