President Donald Trump is enjoying 90 percent approval ratings within his own party, but potential Republican challengers see a possible opening if he's dragged down by scandal and investigation.

The Republican National Committee passed a resolution in January declaring “undivided support” for the president after merging the party and Trump's re-election campaign, but at least three Republicans are weighing a possible challenge, reported the Los Angeles Times.

“What are they so afraid of?” said Maryland’s Republican Gov. Larry Hogan, whose visits to Iowa have sparked rumors that he will challenge the president. “It’s like we have to swear allegiance to the ‘Dear Leader.’"

Hogan, who has denied he will seek the GOP nomination, doesn't see the harm in a primary.

“Why don’t you let us go out there?" Hogan said. "Let people go out there, and challenge and get their brains beat in [if] you’re so all powerful?”

Hogan will also visit New Hampshire, which holds the nation's first primary, later this month, and former Massachusetts governor Bill Weld has formed an exploratory committee and made TV appearances, and former Ohio governor John Kasich is also considering another run at the GOP nomination.

“Plenty of people come and say, ‘Please run,’ so we could put some torpedoes underneath the water line,” said John Weaver, a Kasich advisor and Trump critic. “But those people have never been through a presidential campaign and don’t know how hard it is.”

The would-be challengers see a possible opening if any of the political and criminal investigations turn up evidence that fatally wounds Trump's presidency, and the president has a habit of covering himself in controversy.

Only four presidents have faced serious primary opponents since 1968 -- Democrats Lyndon B. Johnson and Jimmy Carter and Republicans Gerald R. Ford and George H.W. Bush -- and each of them was so badly damaged by the challenger that they failed to win a second term.

White House associates say the president is more focused on his potential Democratic rivals than a GOP challenge, a lot can change before next year's primaries.

“In four, five, six months, Republicans may be happy there’s another option," said Craig Robinson, a former Iowa Republican Party strategist who publishes a blog on GOP politics.