Ok first grab a towel and don't panic! Sorry couldn't help it us old people will get the reference.
But in all seriousness don't panic. Do typo's happen? Yes. Is it the end of it all? No.
Yes you're choosing a path where the drill into you from day one attention to detail but the most important part is how you handle the mistake after it happens.
Are you going to sit there and worry yourself sick or are you going to call the Senator's office and see if there is something you can do? See the difference?
You also have to balance that with is it a huge mistake, like you typed your name wrong. Or a little one like you used the wrong word(i.e. to, too, two) just once.
If it's huge call, if not don't.