Don’t cross President Donald Trump.

That’s the lesson being learned by Republicans after Trump critic and GOP Rep. Mark Sanford lost his primary election in South Carolina hours after the president tweeted that he was “very unhelpful.”

It’s a cautionary tale for Republicans in Congress as they try to win elections by showing loyalty to Trump supporters while also maintaining some independence as members of a co-equal branch of government. One wrong turn — or in Sanford’s case, many — and they could endure the wrath of a president who is quick to attack detractors as enemies, even those from his own party. A single presidential tweet can doom a career.

Sanford is the second incumbent House Republican to lose a primary this year — and the latest victim of intense divisions among the GOP in the Trump era.

The president took a victory lap on Twitter early Wednesday, touting his success in ousting a foe and reinforcing, once again, that the Republican Party is Trump’s party now.

“My political representatives didn’t want me to get involved in the Mark Sanford primary thinking that Sanford would easily win – but with a few hours left I felt that Katie was such a good candidate, and Sanford was so bad, I had to give it a shot. Congrats to Katie Arrington!” the president said on Twitter.

House Speaker Paul Ryan downplayed the riff Wednesday and said there’s always going to be winners and losers during primary season.

“This happens,” said the speaker, who is retiring rather than seek re-election. “That’s just what happens in contested primaries.”

Others, though, said it’s an up-close example of how not to publicly criticize the president over differences.

Trump ally Rep. Chris Collins, R-N.Y., offered advice to fellow GOP lawmakers: Say something nice to the president before you bring him your complaints.

“I would start by praising the president — what he’s doing in North Korea, what he’s done on tax reform, what he’s done with the Supreme Court … and then say, ‘But here’s an issue in my local area where I have some disagreement or I’d like to be something different,'” Collins said.

He said talking to Trump should be like interactions with your spouse or children when you have a problem that needs airing. Start with niceties before bringing up the trouble spots, “as opposed to just coming out with smashmouth football.”

House Republicans otherwise were upbeat Wednesday after primary elections in several states as they met behind closed doors to discuss the coming midterms.

“It’s not like people live in fear of the White House,” offered Rep. Tom Cole, R-Okla., a veteran GOP strategist. “You have to handle all your differences with anybody professionally, and hope for the best.”

(AP)