BISMARCK, North Dakota (AP) — Republican Rep. Kevin Cramer of North Dakota got a hard sell last week from President Donald Trump, who gave Cramer and his wife a personal tour of the West Wing and used the gilded luster of the newly renovated Oval Office to entreat Cramer to challenge popular Democratic Sen. Heidi Heitkamp.

It didn't work: Cramer turned down Trump, who had also called him about the race last fall.

It's the latest in a string of complications for Senate Republicans, who are clinging to a paper-thin majority and entering a midterm election year saddled with Trump's low approval r...