Donald Trump made a noticeable change that signifies his campaign has entered a new era

Clinton ridicules Trump
Clinton ridicules Trump

The day after Donald Trump fired his campaign manager, the first signs of a major shift in strategy started to emerge.

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While Hillary Clinton was speaking in Ohio, the Trump campaign blasted out emails with responses to her barbs.

The presumptive Republican nominee for president deployed the rapid-response messages from several platforms. He — or his campaign — tweeted, posted a video on Instagram, and sent emails while Clinton was still onstage speaking.

See Trump through the years:

This type of rapid response is a common tactic of Clinton's campaign. But until now, the media hasn't seen anything on a similar scale from Trump.

In her speech on Tuesday, Clinton criticized Trump's business record and challenged his plan for the US economy.

"He's written a lot of books about business," Clinton said. "They all seem to end at Chapter 11."

During the speech, the Trump campaign sent out emails with subject lines like "The Catastrophic Economic Record Under Clinton-Obama Policies" and "Trump Economic Plan Will Create Millions Of Jobs & Trillions In New Wealth."

Trump also sent out a series of tweets, although it's unclear if he was personally crafting the messages or if his campaign was tweeting from his account:

The tweets seemed less off-the-cuff than usual and were missing Trump's typical monikers for his rivals. He often refers to Clinton as "Crooked Hillary" in his tweets.

Trump's campaign also sent out its first fundraising email on Tuesday amid reports that Trump was falling far behind Clinton in raising money.

A recent Federal Elections Commission filing revealed that Trump ended May with only $1.3 million in cash on hand. Clinton, in comparison, had $42.5 million.

Up until now, analysts have often observed that Trump hasn't run a traditional campaign operation. He often boasted about self-funding his campaign during the Republican primaries, he's relied more on free media appearances and rallies than he has on television ads, and he employs far fewer people than Clinton.

But Trump has been falling behind in the polls as the election cycle shifts from the primaries to the general. And now the pressure is on for Trump to prove that he can compete against an establishment candidate like Clinton.

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In his first step toward a new direction, Trump fired his campaign manager Corey Lewandowski on Monday.

Lewandowski was reportedly a polarizing figure within the campaign, but Trump had stuck by him even after he was charged with battery for grabbing a reporter at a campaign event. Trump also insisted on keeping Lewandowski on even after he appointed Paul Manafort, a more experienced political operative, to be the campaign's chief strategist.

But Trump's loyalty to Lewandowski came to an end as he announced that he would start running a "different kind of campaign" — one that seems more professional.

Lewandowski had a reputation for his temper and lack of experience on the national political stage. He was also known for saying "Let Trump be Trump," a laissez-faire motto that could prove dangerous for a candidate who's facing a more polished competitor in a general election.

"We ran a small, beautiful, well-unified campaign. It worked very well in the primaries," Trump said on Fox News' "The O'Reilly Factor." "But we're going to go a little bit of a different route from this point forward."