A couple Never Trump Republican electors could vote for Harris instead, only a minority of states have laws that discount their electoral college votes from memory

In 2016:

In Washington, Democratic Party electors gave three presidential votes to Colin Powell and one to Faith Spotted Eagle

In Hawaii, Bernie Sanders received one presidential vote and Elizabeth Warren received one vice-presidential vote.

In Texas, Christopher Suprun voted for John Kasich for president and William Greene voted for Ron Paul, giving each one presidential vote.

On election night, Trump won 306 electors and Clinton 232. However, because of seven faithless electors (five Democratic and two Republican), Trump received 304 votes and Clinton 227.