By confirming Kavanaugh, the Republican-controlled Senate would cement the court majority conservatives have dreamed of. But that could also make it less likely that the Senate will remain in Republican control, strategists in both parties say.
By defeating Kavanaugh, the Senate would leave the court seat open with no guarantee that Trump could install another strong conservative to replace retired swing-vote Justice Anthony Kennedy. But Kavanaugh's defeat could simultaneously diminish the odds that Democrats recapture a majority and seize control of the Senate agenda.
That's a different political calculus than existed a month ago, before Christine Blasey Ford went public with her allegation that Kavanaugh sexually assaulted her when they were teenagers. (Kavanaugh vehemently denies the allegations.) Then, when the Kavanaugh nomination fight was a traditional ideological clash, Republicans saw winning as the minimum necessary to preserve morale among conservatives' base in an otherwise dispiriting midterm election season.
Now, the politics of grievance has turned that around. The hearings last week, in which both Kavanaugh and defenders like Sen. Lindsey Graham raged against what they call character assassination, brought a new level of emotional intensity to the Republican campaign.
In recent days, pollsters have reported rising interest in the election among rank-and-file Republicans. That has narrowed the "enthusiasm gap" that all year has benefited Democrats outraged by the Trump presidency.
Emotional intensity produces voter turnout. The challenge facing Republicans is preserving it for the remaining four weeks of the campaign.
Confirmation of Kavanaugh on the Senate floor in the next few days may sap that intensity. Like politicians and the news media, voters have short attention spans.
But a defeat at the hands of Democrats and moderate Republican defectors would heighten the belief of conservatives that they remain under siege in American culture even as the GOP controls Congress and the White House. For Republican campaign strategists, that's political gold.
Trump's recent remarks suggest he senses that emerging dynamic as well. Ignoring advice from Senate GOP leaders, he mocked Ford at a campaign rally this week. He has also described Kavanaugh's past "difficulty" with alcohol in ways at odds with Kavanaugh's description of himself.
The Kavanaugh rally appears insufficient to salvage the Republican majority in the House. The Cook Political Report now projects gains of 25-40 seats for Democrats, who need 23 to gain control. Many battleground House races take place in moderate suburban districts, where opposition to Trump among college-educated white women has given Democrats the upper hand.
The Senate battleground is far different. Needing to gain two seats for control, Democrats must defend vulnerable incumbents in Trump-friendly states such as North Dakota, Missouri, Montana, Indiana and West Virginia. With most races close, an uptick in GOP turnout fueled by anger over Kavanaugh's fate could tip the balance.
It could even help Republicans here in Florida, where Gov. Rick Scott seeks to oust longtime Democratic Sen. Bill Nelson.
Florida retains its status as the largest swing state in the country. It features eight competitive House races in addition to the tossup Senate contest.
Nelson, the blandest of politicians, has taken a narrow lead. He benefits from the Democrats' nomination of an African-American candidate for governor, Andrew Gillum, which promises to boost turnout among black voters.
Now, Republicans envision an offsetting boost from conservatives irate over Kavanaugh — but only if he is denied the Supreme Court seat.
"The best thing to happen for Republicans in the midterms would be for Kavanaugh to be defeated or forced to withdraw," said Mac Stipanovich, a veteran Florida Republican strategist. The converse is also true. If Republicans elevate Kavanaugh to the Supreme Court despite sexual misconduct allegations, Democrats gain a last-minute burst of grievance.
Election Day is 33 days away.