He may have less need for the enabling act, or abolish electoral politics in a slightly different way. In this scenario he may just be able to rule through Article 48 for life. In a scenario where he's popular enough to win the election, the NDSAP would probably still be the largest party in the Reichstag, so Hitler could just appoint a Nazi chancellor that would do whatever he wants. The quasi legal means by which a democracy dissolves itself would influence the development of "militant democracy" in political science later on in the 20th century. It's essentially the idea that democracy is more than a neutral procedural tool, the definition of democracy expanded to include democratic values that the state has to defend against ant-democratic movements.
This sounds like a difficult POD to pull off, Hindenburg was a popular war hero with the general public who had the support of the Weimar coalition parties as well. Without something crazy like Hindenburg's assassination during the campaign, Hitler outright winning the presidency is difficult to pull off.
