when he says "Because if that were true, someone should have said something before now" he is saying that if indeed you had to be thirty-five to be a senator, someone should have told him earlier.
when the lady says
"My point exactly. Look into it. You'll see I'm right"
She is reassuring him that it is indeed a requirement to be thirty-five to be a senator, and that he should look up to confirm it. Upon doing so, he will see that she was right.
"dialed the smile up to full strength"
this means that the smile she had went from a small smile, to a big smile :) -> :D