Former White House senior adviser David Plouffe warned Democrats that their loss in a special election last week is a “screaming siren” they need to work harder heading into the midterm elections.

“We have a turnout issue,” Plouffe said in an interview with Bloomberg Television. “This is a screaming siren that the same problems that afflicted us [in 2010] could face us again.”

Democrat Alex Sink lost the congressional special election in Florida last week to Republican David Jolly by about 2 percentage points. Attacks on ObamaCare figured prominently in the campaign, but Plouffe said the problem was a “turnout issue.”

Democrats were thought to have a technological advantage in the 2012 campaign, but Plouffe said that is not enough to get people to turn out.

“It’s not just about data and technology,” Plouffe said. “The candidates themselves are going to have to do a good job inspiring them.”

Plouffe’s acknowledgment of the “screaming siren” stands in contrast to many other Democrats, who have tried to play down the loss.

The Democratic Congressional Campaign Committee called the electorate “heavily tilted towards Republicans” in a memo the night of the loss.