How the Presidential Election Got This Close

As Donald Trump turns to obscenity, racial disparagement and sexual innuendo to blunt Kamala Harris’s surge in the polls, he faces a daunting obstacle: the intense hostility among Democrats to all things Republican.

How so?

Harris has consolidated support from key Democratic groups — the young, Black voters, women, Hispanics — who were lukewarm on Biden.

These voters share with their fellow Democrats a deep animosity to the Republican Party. They are inherently distrustful of Trump and highly unlikely to switch their allegiance to him.

The same logic works in reverse.

Since Biden’s withdrawal from the race, Trump’s standing in the polls has remained consistently firm in the 45-to-48 percent range — a bloc of voters seemingly impervious to criticism of their chosen leader.

Just as the overwhelming majority of Harris’s supporters won’t flip to Trump, Trump’s support is firmly entrenched, effectively creating a ceiling on Harris’s ability to extend her current modest lead.

The American electorate, as Lynn Vavreck, a political scientist at U.C.L.A., and her co-authors wrote, has “calcified.” Polarization doesn’t just pull us apart; it holds coalitions together.