Tucker leaving North Carolina's US Senate race

Tucker was calling supporters Monday with the news, and a "Dear Friend" email went out Monday afternoon explaining his decision.

Tucker announced a challenge against Tillis earlier this year, and the two were already advertising against each other in what was expected to be an expensive GOP primary. But Tucker's email said the race had become too much about President Donald Trump, who endorsed Tillis, and that the ongoing impeachment proceedings in Washington, D.C., "sucked the oxygen out of our campaign discussion and greatly curtailed our fundraising ability," galvanizing Republicans and Democrats alike for incumbents.

"It has been increasingly difficult to engage voters on Tillis’ Senate record and to raise campaign money," the letter states. "Any access of our campaign to national conservative funding has been effectively cut off by the impeachment proceedings and by Trump’s endorsement."

Tucker had already put $1.6 million into the campaign, the majority of his fundraising. He said in the letter that he couldn't fund things at that level going forward and that he expected it would cost an additional $2.5 million to finish the primary race.

'We've got a good story to tell,' Tillis says of his re-election plans

Tucker's decision comes the week campaign filing begins in congressional races, and for now, it leaves Tillis to face Sandy Smith, whose candidacy is not nearly so well funded, in the primary. At least three Democrats are running for the seat: former state Sen. Cal Cunningham, who held formal campaign kickoff events around the state Monday; state Sen. Erica Smith, D-Northampton, and Mecklenburg County Commissioner Trevor Fuller.

Tucker closed his letter by saying "the conservative principles which we stand for will ultimately prevail." He gave no indication that he'll endorse Tillis, saying "impeachment has provided an ideal issue for Tillis to whitewash his record of flip-flops."

Tillis' campaign manager said in a statement that it's time to "turn our attention to building the diverse coalition necessary to defeat whichever radical, liberal nominee the Democrats put forward in March."