Dem 2020 nominee must focus on issue other than Trump, says political scientist

Political scientist Michael Cornfield said on Wednesday that the Democratic nominee in 2020 will ultimately need to focus on an issue other than President TrumpDonald John TrumpGrassroots America shows the people support Donald Trump Trump speaks to rebel Libyan general attacking Tripoli Dem lawmaker: Mueller report shows 'substantial body of evidence' on obstruction MORE on the campaign trail. 

"The presidential campaign trail is littered with the carcasses of people who tried to defeat Donald Trump by running against him, instead of for something, on their own issue," Cornfield, the director of the GW Politics Poll, told Hill.TV's Joe Concha on "What America's Thinking."

"Whoever wins the Democratic nomination will be the one who articulates a vision, and has an appealing personality, but above all, has warned that American people that, 'hey, we're ignoring this. We need to take care of this,'" he continued. 

Cornfield's comments come hours after Republicans maintained control of the Senate, but lost their majority in the House in the midterm elections. 

The elections were widely interpreted as a referendum on President Trump's first two years in office. 

Trump on Wednesday appeared to be happy that Republican House incumbents who distanced themselves from him, such as Reps. Carlos Curbelo (Fla.), Barbara Comstock (Va.) and Mia Love (Utah), were all defeated.

The conclusion of the midterms has led to further speculation on who will challenge Trump in 2020. 

Potential challengers include former Democratic Vice President Biden, as well as Sens. Elizabeth WarrenElizabeth Ann WarrenThe Hill's Morning Report — Mueller aftermath: What will House Dems do now? Warren spends big on staff in high-stakes 2020 gamble On The Money: Inside the Mueller report | Cain undeterred in push for Fed seat | Analysis finds modest boost to economy from new NAFTA | White House says deal will give auto sector B boost MORE (D-Mass.) and Bernie SandersBernard (Bernie) SandersGrassroots America shows the people support Donald Trump Five former Obama ambassadors back Buttigieg Both sides were wrong about Mueller report, and none of it will likely matter for 2020 MORE (I-Vt.). 

— Julia Manchester