Donald Trump is doing himself a disservice by failing to use all the tools of a modern election campaign, Democratic strategist Michael Feldman said Wednesday.
"Trump is not taking this seriously," Feldman told CNBC's "Squawk Box."
Much of Trump's staff is new to the game, and the outspoken businessman has alienated campaign veterans within his party and left them sitting on the sidelines, said Feldman, a partner at Glover Park Group.
Trump has also said the data-driven approach that helped President Barack Obama win the White House in 2008 and 2012 was "overrated." He said he would not invest much in similar operations and instead continue to rely on his rallies to get his message out.
Feldman said it is "amazing" that Trump has attracted up to 40 percent of the Republican vote. He said Trump possesses political instincts and an ability to project a broad message unlike anything he's ever seen, but that won't carry him through November.
"He cannot win a general election if he doesn't actually start treating this seriously," he said.