Mr. Biden’s biggest concern remains his lagging enthusiasm numbers. Polls consistently show the majority of Democratic voters notably unexcited about his candidacy. One fix would have been a running mate hailed as a fresh and rising Democratic star. Ms. Harris has alienated key elements of her party, in particular progressives who despise her as a “top cop” from her six years as California’s attorney general. In a poll this week by the Economist/YouGov, Ms. Harris was viewed favorably by only half of African-Americans and very favorably by only 26% of liberals. Will that keep people from pulling a Biden-Harris lever? Maybe not, but she won’t likely be a poll driver.
And there’s still a possibility she’ll do harm. Mr. Biden’s age and questions about his mental acuity guarantee an outsize focus on his running mate, who could end up president. Ms. Harris’s own presidential run proves she has a propensity to make mistakes—potentially big ones. The Trump campaign is eager to define her as a Bernie Sanders liberal, and she’s got a track record that helps—having endorsed Medicare for All, the Green New Deal and gun bans. Many Americans will also remember her leading role in the character assassination of Justice Brett Kavanaugh, matched only in political theater by Cory “Spartacus” Booker. This has the potential to turn off some suburban and independent voters. Even if they don’t rush into Mr. Trump’s arms; they may simply not vote.