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.
Feldman spoke after Hillary Clinton claimed the Democratic nomination in a speech on Tuesday night after winning a number of primaries.
Clinton, the first woman to clinch the nomination of a major party, chose the right moment to emphasize the historic nature of her achievement, Feldman said. She also drew contrasts with Trump and attempted to draw in supporters of Sen. Bernie Sanders, he added.
"That was strategic. It was smart. It was an impact moment. Campaigns for president are really hard. In order to win, you've got to be intentional, and you've got to find moments like this, and actually make an impact on voters. She did," he said.
Still, no one in the Clinton campaign is discounting Trump, he said. He acknowledged that Clinton is clearly the establishment candidate in a highly anti-establishment cycle.
Also on "Squawk Box," Republican Tony Fratto said it would be easy for the GOP to take the White House if it had a candidate who could credibly attack Clinton, who is highly unpopular and campaigning under the shadow of an investigation into her use of a private email server during her tenure as secretary of state.
Instead, he said, Clinton is running against someone who has been criticized by other Republicans for what they called racist comments about the Mexican-American judge presiding over a case involving Trump University.
"The Republican party — we have to understand this — is a minority party. We have a hard time winning when we're unified. If we lose 2 or 3 or 4 percent of the vote in a general election, it's a landslide for Democrats," said Fratto, deputy press secretary under then-President George W. Bush and now a partner at Hamilton Place Strategies.
Trump has said he plans to deliver a speech next week in which he will criticize Clinton for allegedly exploiting her position as secretary of state to enrich herself and Bill Clinton by soliciting donations from influential foreigners to the Clinton Foundation.
Republican Lanhee Chen said the topic is a smart move because there is no greater unifying force among Republicans than their opposition to Clinton. Trump also has an opportunity to attract the disaffected, white working class voters who supported Sanders, he added.
"The difficulty though is his behavior in the last two weeks, his comments about the federal judge, his inability to put together a campaign that is prepared to win this November worries a lot of Republicans," Chen told CNBC's "Squawk on the Street."
"He's got some holes in the dam that are letting through water," said Chen, a research fellow at Stanford University's Hoover Institution.
Thus far, Clinton has been playing chess, while Trump has been playing dodgeball, former Obama campaign adviser Mark Hannah said Wednesday.
If Trump wants to win over independent moderate voters with the speech, he must do it on substance and by articulating his policy, said Hannah, a lecturer at The New School.
"So far we haven't seen he has the ability to do that. He is engaging in this politics of personal demonization, destruction," Hannah told "Squawk on the Street."
"By going after the most frivolous things, the most sort of superficial, childish things, calling her names, is not necessarily going to woo independent voters, who are sick of this kind of politics," he said.