I was initially unconvinced that he'd be able to pull voters from Biden, but then I realized how heavily he's leaning on religious sentiments, and his choice of running mate bolsters that.

It's not a stretch that he can appeal to some Biden voters by playing that so heavily. He's much more sincere in that belief than Trump is. Having an actual pastor as his VP could be enough to galvanize the religious zealots in Trump's base.

His visability, money, the religious platform, etc, is more than enough that he shouldn't be underestimated as a threat to Biden.