The conventional wisdom about the 2018 midterm elections is that the Democrats have a far better chance of winning a majority of the House than the Senate, and I have no reason to question it. The Senate election map is soaked in red, with 10 incumbent Democrats running for re-election in states that Donald Trump won two years prior. Only one incumbent Republican is in the reverse position. This is partly why we see much more Democratic energy invested in House races; it’s the lower-hanging fruit.

Yet Democrats would be foolish to write off the Senate. They only need to net two seats to gain a majority, and the community of professional handicappers has classified just enough races as tossups to make that dream possible.

Moreover, while control of the House would blunt Trump’s legislative agenda and rev up congressional oversight, control of the Senate gives Democrats the power to slow, if not stall, Trump’s quest to stack the judicial branch with conservatives. Not only would Democrats be able to block lower court nominations, but any retirement thoughts from Clarence Thomas would probably get shelved.

With rank-and-file Democrats increasingly panicked about the judiciary drifting rightward, you might expect them to empty their pockets to seize the Senate. But the House is where Democrats are spending most of their money. Case in point: The Democratic Congressional Campaign Committee, the party’s official House campaign arm, has raised double the amount of the Democratic Senatorial Campaign Committee. (The DCCC typically raises more than the DSCC, but not that much more.)

This is not to say the Senate Democratic candidates are starved for cash. Most of the vulnerable ones have outraised their Republican opponents, and three have broken records in their states. (A notable exception: Florida incumbent Sen. Bill Nelson, who is facing free-spending, independently wealthy Republican Gov. Rick Scott.) But considering how uphill the Senate battle is for Democrats, they are going to need every last dollar, as well as every last volunteer.

Yet it may be hard for Democratic small donors and activists to generate the same level of enthusiasm for their Senate field as their House field. Why? The House lineup is teeming with fresh faces, including a huge influx of women and military veterans with sterling resumes. And the contingent of “Berniecrats” organizing to push the party leftward are excited for candidates who could prove the potency of their platform, such as Nebraska’s Kara Eastman and New York’s incumbent-slayer Alexandria Ocasio-Cortez.

But the Senate? The first order of business is to defend a bunch of weathered incumbents—exactly the kind of moderates whom Ocasio-Cortez and her allies are trying to purge from the party. Senators like Montana’s Jon Tester and Missouri’s Claire McCaskill aren’t running as card-carrying members of the Resistance. They are running as bipartisan, independent-minded problem-solvers. Some tout (perhaps even exaggerate) their working relationships with Trump. And the few Democrats mounting credible campaigns for Republican-held seats are largely running in a similar bipartisan mold, particularly Arizona’s Kyrsten Sinema and Tennessee’s Phil Bredesen.

Any attempt to drum up excitement for the slate of Senate moderates will likely soon be doused by the Supreme Court nomination of Brett Kavanuagh. Chances are many of the red staters will end up voting “aye,” especially if no Republican breaks ranks, making his confirmation a certainty anyway. Such a vote will be politically necessary for vulnerable Democrats to square with their own bipartisan campaign rhetoric, but will anger Democratic base voters, and further incentivize them to steer their energies towards the House.

But progressive voters should not assume that just because these red state Democrats take a strategic—and in all likelihood, non-determinative—Supreme Court vote, they can never be relied upon and therefore aren’t worth saving. If Democrats are to have any hope of throttling the Republican march on the judiciary, they need the Joe Manchins and Doug Joneses of this nation to occupy Republican territory, as well as get additional reinforcements. That’s going to require swallowing the occasional annoying vote.

One Senate Democratic challenger who is firing up the progressive base is Texas Rep. Beto O’Rourke. While his bid is considered a long shot by professional prognosticators, and he has banned political action committee donations, in the last three months he has raised more than twice as much the incumbent, Ted Cruz, thanks to a huge network of small-dollar donors.

How is that possible? O’Rourke is charismatic. His represents generational change, exemplified by his penchant for live-streaming his many cross-state campaign car trips. He is running a decidedly liberal campaign (albeit with bipartisan flourishes), offering the chance to prove that authentic ideological conviction can turn a red state blue. And he is running against a perfect villain in the caustic conservative Cruz. An O’Rourke upset would taste far sweeter to the left than protecting the bland Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota or Bill Nelson of Florida.

Democrats need not treat the midterms as a zero-sum game. They can and should invest in both the House and the Senate, shore up vulnerable incumbents and place bets on long shots, and support candidates of the left and candidates of the middle.

However, as campaign activity becomes more driven by grassroots individuals and less by party machinery, money and time naturally gravitates toward the more exciting candidates, the fresh faces, the compelling back stories and the viral videos. But if Democrats are going to take the Senate, they will need to protect a group of candidates who offer none of the above.