Missouri Attorney General Josh Hawley announced Monday evening that he is running for Senate in 2018. The young Republican may prove the most formidable challenger yet to Claire McCaskill, who is widely seen as one of the Senate’s most vulnerable Democrats.

Hawley, who is popular and well-connected in Missouri, enters the race an instant frontrunner in the Republican primary. In his announcement video, Hawley skips straight to his general election pitch: that McCaskill, a two-term incumbent, is out of step with his state’s values.

“Senator McCaskill, she’s been in D.C. forever,” Hawley says in the video. “She’s turned her back on farmers, she’s ignored working families, she’s been wrong on every Supreme Court nominee for 11 years. She doesn’t represent us.”

State Republicans are desperately hoping to avoid a repeat of their 2012 debacle, where a fractious GOP primary and serial gaffes by nominee Todd Akin led to an easy reelection for McCaskill. Congresswoman Ann Wagner’s July decision not to seek the Senate made some hopeful for a smooth primary.

“We were facing . . . a decent possibility, maybe a 50-50 possibility, of an expensive primary fight,” GOP strategist Gregg Keller told Roll Call at the time. “I think the chances of that are lesser and therefore Republicans are in a better spot.”

But Hawley, who won the attorney general job by 17 points last year, will face a daunting challenge: bridging the gap between supporters of Donald Trump and state moderates who have been some of his biggest boosters in the past.

Hawley has already found himself a flashpoint in tensions over the president: When Trump announced plans to visit Missouri in August, former senator John Danforth, a Hawley supporter, wrote an op-ed condemning him as a “hateful man” and “the most divisive president in our history.” Danforth called on Hawley to denounce Trump; pro-Trump figures called on Hawley to denounce Danforth. Hawley did neither.

We'll see if he can continue to straddle that line.