Hi,

I would not prefer that you leave it leaning as the lip of the seal is stretched tighter not being in a complete circle around the shaft.
The lip is stretching to a larger diameter and back to the size it was made for.
These sets up a fast wiggle at speed that might creep the seal loose and the oil travels with the shaft in a straight line and will dam up on one side.
Depending on velocity it will eventually seep under the lip more than it was designed to hold back. The wiggle is a flutter up and down and back and forth.
In other words, it’s life will be shortened, let along where the oil goes and touches.

In lots of cases I have seen that there is enough space to the rear to put in two seals on lots of equipment.
Like on the red block, the front lowest crankshaft area can hold two seals in there. You can move that one pretty far back if need be to clear a worn in groove or scratches. Just be careful not to hit the crankshaft shoulder.
I’m not sure about the upper two front seals if their deep enough.

Anyway, pulling it is the best and try to use that old one to help you push in a new one.
Reverse the old one so you get more surface area to push in with!
You will be able to see how straight you are moving in as it will stick out farther.
If need be, You can tap the old one and not damage the new seal.

Live and learn or why would have I know this!
It happens!

(:))
Phil