President Trump invited Sen. Heidi Heitkamp (D-N.D.) onstage at a tax speech in North Dakota on Sept. 6, calling her a "good woman," and saying "I think we'll have your support" on tax cuts. (The Washington Post)

MANDAN, N.D. — A year from now, North Dakotans may be hearing these two words a lot: “Good woman.”

The man who uttered them was President Trump, who on Wednesday made his maiden trip to North Dakota as president to pitch his tax reform plan and, it turned out, compliment the state’s embattled Democratic senator, Heidi Heitkamp.

As the president mentioned the state’s elected officials, he invited Heitkamp to join the Republican lawmakers on stage with him. “Come on up, senator,” he said, motioning to Heitkamp. “These are great people. They work hard. They’re for you, 100 percent.”

As Heitkamp stepped onto an outdoor catwalk at an oil refinery here in Mandan to join him onstage, Trump delivered play-by-play commentary.

“Everybody’s saying, ‘What’s she doing up here?’ ” Trump said. “But I’ll tell you what: Good woman.”

The president punctuated his praise with a friendly handshake. And with that, Heitkamp had the makings of a potentially powerful advertisement for her reelection campaign next fall, when she plans to make a bipartisan appeal to keep her seat in this reliably Republican state, which Trump carried in 2016 by 36 percentage points.

Heitkamp traveled aboard Air Force One with Trump from Washington, along with the state’s other U.S. senator, John Hoeven, and its lone House member, Kevin Cramer, both Republicans.

The White House trumpeted Heitkamp’s participation in Wednesday’s trip as evidence of bipartisan support for Trump’s plan to overhaul the tax code. But although Heitkamp has spoken favorably about tax reform in general terms, she has not explicitly endorsed Trump’s agenda. The president has yet to detail his plan in legislative form.

Heitkamp did not speak at Trump’s event, but she issued a statement Wednesday evening saying that "it was good for our state" to hear the president articulate his plans.

"Today President Trump spoke about his priorities for tax reform, and it’s encouraging he committed to promoting American workers as key to any tax reform policy," Heitkamp said. "But, as North Dakota’s former tax commissioner, I know the devil is in the details of any reform plan as tax codes are complex, and we need to know what those details are."

Trump bemoaned the current tax code as “a giant, self-inflicted economic wound.” But the president’s remarks, like his speech on taxes last week in Springfield, Mo., was short on policy substance and heavy on rhetoric and style.

“All told, it will be the greatest tax reduction in the history of our country — greater than ever before,” Trump said. “That’s going to be something. You’ll see a rocket ship. You will see something happen like you’ve never seen.”

Trump held his event at an oil refinery in Mandan, Heitkamp’s home town, just across the Missouri River from Bismarck, the state capital. Trump used the occasion to pressure Heitkamp to eventually vote for his tax bill, noting that the last meaningful tax bill, under President Ronald Reagan in 1986, was passed with the support of North Dakota’s Democratic senator.

“It can happen,” Trump said. “Are you listening, Heidi? Yes, Heidi’s listening.”

The president then teased Heitkamp, saying, “I’m not putting her on the spot.”

Then he delivered his threat, which was intended for all of Congress, not Heitkamp specifically: “Do your job to deliver for America or find a new job. Do something else. Just do something else.”

Johnson reported from Washington.