(CNN) Rep. Kevin Cramer, the Republican challenging Sen. Heidi Heitkamp this fall in North Dakota, compared voting against President Donald Trump in Congress to cheating on a spouse.

Cramer's comment criticizing Heitkamp's voting record came in a Wednesday radio interview with conservative North Dakota host Scott Hennen.

"Here's the good news about Donald Trump: Most of the time, he's for North Dakota, and that's my point where I've heard her say, 'Gee, I voted with him 55% of the time,'" Cramer said.

"Can you imagine going home and telling your wife, 'I've been faithful to you 55% of the time?' Are you kidding me? Being wrong half the time is not a good answer."

Cramer is closely aligning himself with Trump, who cruised to a 36-point victory in North Dakota in 2016. But the comment is an awkward analogy, given Trump's long and well-publicized history of marital indiscretions. Stormy Daniels, an adult film actress, has said she was paid $130,000 days before the 2016 election by Trump lawyer Michael Cohen to keep quiet about a 2006 affair. Trump has denied the affair with Daniels.

Asked to explain his comments, Cramer said in an email: "I was clearly talking about Heidi Heitkamp's attempt to hide from her voting record by claiming she supports the Trump agenda. Voting in the best interests of North Dakota 50% of the time is nothing to celebrate. One vote does matter in the US Senate. She voted against tax reform. She voted to fund sanctuary cities. She even voted to allow late-term abortions. These are not North Dakota's values."

Heitkamp's campaign criticized the remarks, accusing Cramer of putting loyalty to Trump ahead of the state's interests.

"Loyalty to North Dakotans ought to come first every time -- that's what Heidi believes, but Congressman Cramer believes that being a faithful vote for President Trump and his party are more sacred than the interests of North Dakota families," Heitkamp campaign press secretary Sean Higgins said.

Cramer's penchant for off-key remarks was part of why Republicans spent part of 2017 searching for an alternative Senate candidate before settling on him as their best option. Cramer waffled himself, opting against a run this year before changing his mind.

Last year, in a radio interview, he criticized Democratic women for wearing "bad-looking white pantsuits" to Trump's address to a joint session of Congress in solidarity with women's rights.

"By the way, did you notice how poorly several of them were dressed as well?" he said. "It is a syndrome. There is no question, there is a disease associated with the notion that a bunch of women would wear bad-looking white pantsuits in solidarity with Hillary Clinton to celebrate her loss. You cannot get that weird."

He also raised eyebrows by saying that then-White House press secretary Sean Spicer's analogy between Adolf Hitler and Syrian President Bashar al-Assad is "not without some validity."