Billionaire investor Wilbur Ross stood behind Republican Donald Trump but urged him to stop engaging in exchanges that benefit the Democrats and make the real estate mogul's behavior the issue in the U.S. presidential campaign.

"This election is Donald's to lose and so far the Democrats have been clever about baiting him and he generally has bitten," Ross said in an email to Reuters late on Wednesday.

Ross said Trump's reaction in recent days to criticism by the parents of a Muslim U.S. Army captain killed in the Iraq war "has enabled the Democrats to turn the table and instead of the behavior of the quintessential Washington insider being the issue he is in danger of letting the Democrats make his behavior be the issue."

Ross added, "I assume this will change soon."

A spokeswoman for Trump did not respond to requests for comment.

Ross, who has made billions of dollars betting on bankruptcies and distressed assets, is a critic of Democratic presidential nominee Hillary Clinton's trade views.

The comments by Ross are the latest by Republican politicians and supporters expressing concern over the Trump campaign ahead of the Nov. 8 election against Clinton. Groups of wealthy Republicans unhappy with Trump have been privately courting prominent peers to join them in backing Clinton.

Meg Whitman, a prominent Republican fundraiser, endorsed Clinton on Tuesday.