Katie Hill, 30, is a first-time candidate who may be one of the most impressive Democratic contenders of 2018. The daughter of a nurse and a police officer, she studied nursing herself before shifting to the non-profit sector, and by 29 she was running the largest anti-homelessness non-profit in California, with an annual budget over $40 million. But her ability to navigate a tricky primary may hold the key to Democrats' chances of flipping a critical district.

Republicans' biggest structural advantages in the House — think geography, incumbency and money — have been weakening all cycle. Pennsylvania's GOP map just got thrown out, at least 32 Republicans aren't seeking reelection, and over three dozen GOP incumbents were out-raised by Democrats in the final quarter of 2017 - including GOP Rep. Steve Knight (CA-25), whom Hill out-raised. In the past, these kinds of trends have foreshadowed wave elections.

But as primary season approaches, the explosion of candidate and donor interest on the Democratic side has a caveat: in a lot of races, Democrats suddenly have more well-funded hopefuls than they know what to do with.

In fact, crowded fields of Democrats — there are at least 43 GOP-held seats where at least two Democrats have at least $100,000 in the bank — have become a GOP talking point. According to the Republican narrative, primaries will force Democrats to spend all their money attacking each other and running far to the left. As a result, their nominees will enter the general election bruised, broke and more aligned with the Resistance than swing voters.

So, are these congested Democratic primaries a blessing or a curse? The answer: it depends on the situation, but overall, Republicans shouldn't count on them to save their majority.

First, it's important to remember that competitive primaries didn't stop GOP candidates from winning in 2010 - in fact, many races forced them to hone their skills and helped them get known earlier. Second, for Democrats, nominating a candidate who emerges from a primary broke (a problem that can be fixed) should be less of a fear than nominating a candidate who doesn't fit his or her district (a problem that can't).

Case in point: California's 25th District, located in northern Los Angeles County. As he was in 2016, Rep. Steve Knight is once again one of the most vulnerable GOP incumbents in the House. Knight is a dyed-in-the-wool sophomore conservative with an in-your-face reputation (in 2015, he told a protester "I'll drop your ass") sitting in a district that voted for Hillary Clinton 50 percent to 43 percent. He's also a relatively weak fundraiser known for running low-budget races.

So how did Knight win reelection in 2016 with 53 percent while President Trump lost the district by seven points? And how is he the last Republican from LA County remaining in Congress? The answer: Democrats' star recruit turned out to be a less than ideal fit for the district.

The 25th CD is anchored by northern Los Angeles County and is getting more diverse (38 percent percent of its residents are Latino) and less Republican every year. But culturally, it's worlds apart from downtown Los Angeles. Despite its growth, Santa Clarita likes to think of itself as a small town, and the nearby Antelope Valley is lower-income and heavily dependent on agriculture. Many voters own guns, and a substantial number own and ride horses.

Knight, an Army veteran, former police officer and one-time state senator whose father was famed Air Force test pilot and local politician Pete Knight, has enjoyed strong personal appeal in a district teeming with veterans and LA police officers. His last name and local roots have helped him win twice despite facing better-funded opponents, including Ventura County-based Republican Tony Strickland in 2014 and a Democratic "carpetbagger" last cycle.

In 2016, Knight lucked out when Democrats nominated Bryan Caforio, a partner at a downtown Los Angeles law firm who grew up in upscale Orange County, went to Yale Law School, and moved into the 25th CD to run. Caforio emphasized that his parents were public school teachers, but Republicans mercilessly attacked him as a "Beverly Hills lawyer" propped up by "limousine liberal" donors. It worked, despite Trump's unpopularity.

As a young, female political neophyte, Hill would offer a jarring contrast to Knight, a longtime politician. But unlike Caforio, she wouldn't be susceptible to the carpetbagger label. In fact, she might be Democrats' dream candidate for the down-home, independent-minded 25th CD.

Hill grew up in both the Antelope Valley and Santa Clarita, the daughter of a long line of military veterans. She attended Cal State Northridge, owns guns, and lives with her husband on a farm where they raise horses, goats and chickens. Until recently, she didn't consider herself especially political, but campaigned to pass an anti-homelessness ballot initiative in 2016 and confronted Knight about the GOP healthcare bill at a 2017 town hall.

She's garnered the endorsements of EMILY's List and nearby Democratic Rep. Judy Chu. In the final quarter of 2017, she raised $248,000, slightly more than Knight. She's down-to-earth, talks openly about family members' struggles with addiction and earned praise for sharing the story of her unplanned teenage pregnancy via a Facebook video. She describes herself as a pragmatist who didn't have a strong preference between Clinton and Bernie Sanders in 2016.

There's just one catch: Caforio, 34, is running again in 2018, and he and Hill are vying fiercely to advance to the general election in the June 5 top-two primary. Caforio carries over plenty of name ID from the 2016 race, as well as institutional support from the likes of Lt. Gov. Gavin Newsom and a host of labor unions. Caforio is seeking to run as the "true progressive," and in January won the party pre-endorsement convention with 73 percent of delegate votes.

California's party endorsements aren't binding or especially predictive; after all, Caforio himself beat out a Democratic party-endorsed former LA police officer in the 2016 top-two primary. But according to one private mid-January survey, he narrowly led Hill, likely owing to his residual name recognition. And having been on the ballot before is extremely valuable in a district covered by the cost-prohibitive LA media market where paid communication is limited to digital and mail.

Hill has tied Caforio in fundraising and has almost four more months to close the name ID gap, but Caforio may also feel pressure to attack Hill. For Caforio, who has defended large corporations in major suits, chastising a non-profit executive could risk backfiring. Nonetheless, his campaign could go after Hill's gun collection, skepticism towards full single-payer healthcare or six-figure non-profit salary in an effort to drive a wedge between her and Democratic primary voters.

Another complication for Hill is the candidacy of another female millennial Democrat with a non-profit background, geologist/volcanologist Jess Phoenix. Phoenix, 36, grew up in Colorado and didn't move into the district until recently. She co-founded a science education nonprofit, has appeared on CNN to talk about her candidacy, and has received some money and support from fellow scientists. She's not a top-tier candidate, but could siphon primary votes from Hill.

In 2018, it's possible a handful of second and third-tier Democrats could upset GOP incumbents. But where possible, Democrats would prefer not to take that risk, and CA-25 isn't the only district where Democrats could benefit from nominating someone new.

There are a handful of other districts where very promising, well-funded Democratic candidates in GOP seats must first get past primaries against weaker 2016 also-rans who could derail takeover opportunities. They include Arizona's 2nd CD, California's 21st and 45th CDs, Illinois's 6th and 13th CDs, Kansas's 3rd CD, Michigan's 6th CD, New Jersey's 7th CD, Texas's 7th CD, Virginia's 7th CD. The first test will be Illinois's primaries on March 20.

The Bottom Line: As primary season begins, don't be tempted to buy the narrative that jam-packed Democratic primaries are bound to result in mutually-assured destruction or nominees too far left to win in November. In 2010, both moderates and true Tea Party believers powered Republicans to the majority. For most voters, ideology isn't destiny and 2018 isn't about Hillary vs. Bernie. The bigger risk for Democrats is candidates who are bad cultural fits for their districts.