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 TrumpTrump: WHCA picking non-comedian for headliner a 'good first step' Five takeaways from Mississippi's Senate debate Watergate’s John Dean: Nixon would tell Trump 'he's going too far' 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 WarrenOn The Money: Senate banking panel showcases 2020 Dems | Koch groups urge Congress not to renew tax breaks | Dow down nearly 400 | Cuomo defends Amazon HQ2 deal Election Countdown: Florida fight ends with Scott, DeSantis wins | Dems see Sunbelt in play for 2020 | Trump to campaign in Mississippi ahead of runoff | GOP wipeout in Orange County | Ortiz Jones concedes in Texas House race Sanders on 2020 White House bid: 'We're looking at it' MORE (D-Mass.) and Bernie SandersBernard (Bernie) SandersOvernight Health Care: Drug industry nervous about Grassley | CDC warns public not to eat romaine lettuce | Sanders unveils new drug pricing bill Sanders and Khanna have a plan to lower your drug prices 2020 Democrats challenge Trump's use of troops at Mexico border MORE (I-Vt.). 

— Julia Manchester