It seems like we may never get a straight answer from Democrats about this.

While appearing on Fox News with Bill Hemmer, DNC Chair Tom Perez was doing his absolute best to avoid answering a very simple question that has been raised time and again during this battle over the border: Why aren’t the Democrats supportive of the border measures that Trump is suggesting when they used to be just a handful of years ago?

The conversation started with Perez echoing the Democratic talking point that the border crisis is a manufactured one, and that several agencies agree with him. Perez said that Democrats passed tons of bills regarding border security, and Hemmer agreed.

“You passed a lot of bills. 2013, Schumer voted for more border security. Elizabeth Warren voted for more border security. Bernie Sanders voted for it. 2006, Hillary Clinton voted for it, Barack Obama voted for it; Schumer voted for it again going back 12 years,” Hemmer noted.

Perez decided not to address this, but touched on the point that Democrats care about border security.

“The Democrats believe in meaningful border security,” Perez admitted. “I’m proud of the work I did under Barack Obama to make sure that we were securing our borders and countering violent extremism at home.”

Hemmer wasn’t going to let him off that easy, though.

“So what in the world changed from 2013? What changed from 2006?” Hemmer asked. “What the White House will say, ‘if the president says “purple,” you’ll say “blue,” and it’s really not about policy, it’s about personality.'”

Perez addressed that this wasn’t driven by personality, but still danced around the issue of the Democrats suddenly flip-flopping.

“Again, Democrats have always believed in strong border security but we want smart border security,” he insisted. “Building a wall is not smart border security.” He suggested Obama-era programs like the “Countering Violent Extremism” initiative instead.

The Democrats won’t say it, but the truth is likely a very simple one.

Should Trump fulfill his biggest campaign promise of building a wall then the momentum it would give him and the Republicans in 2020 would be overwhelming, and the loss the Democrats would suffer would stunt their turnover to boot. As Sen. Lindsey Graham made clear, if Trump and the Republicans fail, then they would find themselves demoralized and likely without jobs when the dust of 2020 settles.

The Democrats will need all the momentum they can get going into 2020 and as such will resist Trump with all of their might. This is, however, a rotten hill to die on as the crisis at the border is very real. Even the Washington Post admitted this in an article on Tuesday.