(CNN) - Steve Bullock wasn't going to be the Democratic nominee for president in 2020. So when the Montana governor dropped out of the presidential race Monday morning, it barely made a ripple.
But here's the thing: The big news in Bullock's announcement Monday wasn't that he was dropping out of the presidential race. It was that he wasn't going to run for Senate in 2020 either.
"Governor Bullock will continue to faithfully and effectively serve the people of Montana as their Governor," a Bullock spokeswoman told CNN. "While he plans to work hard to elect Democrats in the state and across the country in 2020, it will be in his capacity as a Governor and a senior voice in the Democratic Party -- not as a candidate for US Senate."
And THAT is a very big deal.
Senate Democrats had long hoped that when Bullock's quixotic bid to be the Democratic presidential nominee ended, he would reconsider his past dismissals of a challenge to Republican Sen. Steve Daines in 2020. And they had some reason to be optimistic! After former Colorado Gov. John Hickenlooper ended his own longer-than-long-shot presidential candidacy, he decided to take on Republican Sen. Cory Gardner in the Centennial State -- handing Democrats a prized recruit in the process.
If Bullock had followed in Hickenlooper's footsteps, it would have been an even larger recruiting coup for Democrats. While Gardner was likely to be a major party target whether Hickenlooper ran or not -- Colorado is one of only two states Hillary Clinton won in 2016 where a Republican incumbent is seeking another term in 2020 -- Democrats are nowhere in Montana without Bullock.
While the state has shown a willingness to elect Democrats to federal office -- Sen. Jon Tester being the most prominent example -- it's quite clearly a Republican state under most circumstances these days. President Donald Trump won Montana by 20 points in 2016 and two years earlier Daines, at the time the state's lone congressman, walked into the open Senate seat with nearly 58%.
To win in a state with that sort of profile, you need something special in a candidate. And that person, for Democrats, is quite clearly Bullock. He spent four years as the state's attorney general before running for governor in 2012. Four years later he was reelected despite Trump winning the state overwhelmingly.
Bullock's moderate profile hurt him in the presidential race but would have clearly been a major asset for him had he taken on Daines. He could have leaned on his eight years as governor as proof positive that he was a far cry from the more liberal national Democratic Party. And he had the built-in name ID and positive ratings among the state's voters to potentially pull it off. (A January 2019 poll showed Bullock with a 60% approval rating, the highest of any elected official in the state.)
What Bullock's no-go decision does, almost certainly, is take Montana off the board of competitive races. (Democrats will likely argue that Daines can still be beaten, but by anyone but Bullock that is a very uphill race.) And that's bad news for Senate Democrats, who are doing absolutely everything they can to widen the potential playing field in their quest to retake the Senate majority come November.
At the moment, the Cook Political Report, a nonpartisan campaign tip sheet, rates just three GOP-held seats -- Arizona, Colorado and Maine -- as "toss ups." Which is somewhat remarkable given that Republicans are defending a total of 23 seats next year. And could bode poorly for Democrats' chances of a takeover unless they can find a way to grow the number of Republicans in danger -- especially when you consider that Democratic Sen. Doug Jones of Alabama is the most endangered incumbent in either party heading into 2020.
To win back the Senate majority, Democrats need to net three seats if their side also wins the White House and four seats if Trump is reelected. If you assume Jones loses, that number goes to four if Democrats win the White House and five if they don't. Which is why expanding the playing field beyond those three most vulnerable Republican seats is absolutely critical. If Democrats swept all three while also losing in Alabama, they would fall short of the majority even if a Democrat beats Trump.
Which is why Bullock's no-go decision on a Senate bid really matters. Even if him dropping out of the presidential race doesn't.