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Hillary Clinton should have one goal tonight: delivering a fatal blow to Republicans down ballot.

This debate probably won’t matter at all for the presidential race. Historically, voters have largely made up their minds at this stage in an election. And their opinions about the candidates tend to harden, not change, in these last few weeks until Election Day.

In the 10 days since Clinton and Donald Trump last debated, Trump has dropped in the polls. That means that the real battle this cycle has shifted down ballot, to the handful of states like Pennsylvania and Missouri that will decide which party controls the Senate for the next two years. In several battleground states, the Democratic candidates have stalled, even as Clinton has pulled ahead of Trump nationally. Katie McGinty has been deadlocked with her Republican opponent in Pennsylvania since August. Catherine Marie Cortez Masto in Nevada and Maggie Hassan in New Hampshire are in similar situations.

No one has more motivation to change that than Clinton. She’s watched the Republicans in Congress obstruct President Barack Obama at every turn—including in the last two years, as the Senate punted on his request for funding in the fight against Zika and refused to consider his Supreme Court nominee. If Clinton fails to engineer a slim Democratic majority in the Senate this fall, her first two years in office could be equally painful.

Tonight is her last, best chance to make this race about more than Donald Trump vs. Hillary Clinton—to highlight the importance of having a Senate willing to at least consider her agenda. She could also start calling out specific Senate candidates who are clinging to Trump. It would be unusual move in a presidential debate, but her advisers are signaling that they are open to it. So keep an eye out for phrases like “the party of Trump” tonight. It’ll mean that Clinton is taking steps to yoke Republican incumbents to the unpopular Republican nominee.