NORTH CAROLINA -- Sen. Thom Tillis has a challenger in the 2020 Republican primary.

Garland Tucker, a retired Raleigh businessman, officially filed campaign paperwork Monday, teeing off a race against the first-term senator.

So, how did North Carolina’s junior senator get in a position to warrant a primary opponent? At least part of it may have to do with the president, who polls highly among Republican voters.

Though Tillis routinely votes with the president, the two have on occasion not been in lockstep, inspiring criticism from conservatives.

Earlier this year, in perhaps the most public example, Tillis wrote an op-ed criticizing the president’s national emergency declaration to build the border wall. Weeks later, facing mounting pressure, Tillis backtracked, siding with the president and voting against a resolution blocking the president's emergency order.

“A lot has changed over the last three weeks -- a discussion with the Vice President, a number of senior administration officials,” Tillis said on the Senate floor explaining his vote.

RELATED: Sen. Tillis Flip-flops, Supports Trump on Emergency Declaration Vote

That episode inspired more murmurs about a potential primary challenger for Tillis. Congressman Mark Walker was floated as a potential challenger, though in statement, Walker's spokesman brushed that aside saying he is “not planning to primary Thom Tillis.”

A recent poll conducted by Morning Consult put Tillis’s approval rating among North Carolina Republican voters at 53% -- the second lowest approval rating among the Republican senators up for reelection in 2020. The same poll showed Tillis’s net approval rating dropped 12 points among GOP voters. The poll was conducted between January 1 and March 31, and has a 1-point margin of error.

Perhaps underlining this point, in an interview with The Washington Post, Rep. Mark Meadows -- a key Trump ally on Capitol Hill and fellow North Carolina lawmaker -- declined an opportunity to endorse Tillis.

“I don’t know that a congressional endorsement -- he’s not asked me for one, I doubt that I would give a congressional endorsement to any senator that it would matter,” Meadows said.

In recent months, Tillis has made multiple public comments defending the president, including at a Senate Judiciary hearing focused on the Mueller report.

“Guys you can go out and spin this any way you want to but the data is there," he said. "There was no underlying crime and there was insufficient evidence to indict the president on obstruction of justice."

Meanwhile, in a statement Monday reacting to Tucker entering the race, Tillis’s campaign manager framed the election as being about Trump loyalty, casting Tillis as the president's ally.

“[Tillis] looks forward to defending President Trump and his policies against any anti-Trump activist who chooses to enter the race. Today's candidate has a long record of attacking the President and appears to be assembling an anti-Trump team,” wrote Luke Blanchat.

The question remains whether running as Trump’s defender is a wise plan in a purple state like North Carolina. While it may poll well among GOP voters in the primary, will it resonate in the general election? 

In a statement, a spokesman for the North Carolina Democratic Party weighed in on Tillis' primary opponent, writing in part, “The rocky start to Senator Tillis’ reelection campaign be traced back to the fact that North Carolinians of all political stripes know they can’t trust him.”

At least four Democrats have expressed interest in running against Tillis, but some analysts argue the national party is still searching for a “big name.”