As Donald Trump runs on the platform "Make America Great Again!," donors giving money to the campaign of the Republican presidential candidate are investing in his message and his ability to win. But with the constant missteps and a big drop in the polls by Trump, those donors are increasingly concerned about a return on investment as they weigh giving more to his campaign. Donors like Victor DeFrisco, 60, an owner of Exit Realty Premier in South Florida, said the time is now to double down on Trump. DeFrisco said he is still behind Trump and hopes the missteps stop. "Hillary's past actions are more harmful than his rhetoric," he said. "I don't think she is beating him. He is beating himself down. He just has to tone down his rhetoric and get back to the issues. But I don't know if he will." DeFrisco who has donated twice to the Trump campaign for a total of $350, vows he is going to donate for a third time in the near future.

Small-business owners like DeFrisco make up a good portion of Trump's donor base, said Steve Mnuchin, national finance chairman for the Trump campaign. Mnuchin also said the Trump campaign will be adding small-business owners to its economic council in an effort to focus on delivering policy solutions to the economic challenges facing small businesses. The Clinton campaign did not respond to CNBC's follow-up inquiry on small-business owner donations for the Democratic candidate.

The latest federal election filings revealed that the GOP presidential nominee's campaign ended June with more than $20 million on hand, a big jump from $1.3 million at the end of May. Clinton's campaign committee reported more than double that, with $44.4 million on hand. The July numbers are expected early Sunday. As an investor in Trump, DeFrisco said it is frustrating to read Trump's tweets and watch his over-the-top comments. He hopes the candidate would listen more to his team, "He is obviously not listening to the donors or his family. He has really good people around him and he is obviously not listening to them," DeFrisco said.

Republican candidate for president Donald Trump speaks to supporters at a rally at Erie Insurance Arena on Aug. 12, 2016 in Erie, Pa. Getty Images

Support from one of Trump's larger donors continues as well. Wilbur Ross, a donor and member of the Trump economic council, said despite the "bumpiness" of the last two weeks, he will continue to support Trump. "The lynchpins of the Clinton economic program simply don't work," said Ross. "We would be left with job-killing increases in taxes and regulation." Added Ross: "Her infrastructure bank would create subprime lending for infrastructure and her energy plan is out of the failed clean energy Obama playbook. So what's left of her economic plan is Obamacare, which is self-destructing before our very eyes."

The rhetoric does concern donors like broadcast billionaire Stanley Hubbard, who recently threw his wallet and support behind Trump. Hubbard who had been a "Never Trump" megadonor, said on CNBC's "Power Lunch," while he doesn't love Trump, he will stand by him. "I am backing him because I don't want Mrs. Clinton picking a Supreme Court justice. We don't need more regulations in our country ... I think Hillary Clinton is more dangerous," said Hubbard. "We know what Mr. Trump is going to do. That is why I am backing Mr. Trump. I am hoping the American people realize, whether they like him or not, Trump would be the best for them." Several high-rolling Republican donors said, under the condition of anonymity, that they while they can't support Trump, they want to support their party and were allowed to earmark their donations to the Victory Fund for the lower tickets and not Trump. The Republican National Committee did not respond to CNBC's request for comment.

"Major donors are concerned with keeping the Senate but not going Trump," said Charles Spies, former chief financial officer and counsel for Gov. Mitt Romney's 2008 presidential campaign. "With Trump on top of the ticket he can't lose by a landslide. Trump must have money or the Senate and House could be lost. The candidates in the key states will be impacted if Trump loses by more than 5 points." Trump on the campaign trail has complained numerous time he has raised money for the Victory Fund but has not seen a lot of that money in return for his efforts.

Trump's slide in the polls comes after the repeated attacks on Khizr and Ghazala Khan, a Gold Star family who lost their son, an Army captain in Iraq. Trump's doubling down on his comments and his tongue-in-cheek call to Russia to find and expose former Secretary of State Hillary Clinton's lost emails have not helped to instill confidence in the candidate.

I believe donors are concerned. This has been disappointing to a lot of people. ... While Trump has disappointed many people with his lack of discipline and off-the-cuff comments, we still hold out hope that he can grow up and get his act together. Gary Emineth former chairman of the North Dakota Victory Fund for Trump