Yes, you give a signature when you vote. I didn't know those were ever compared to anything.
I do think you should have to verify your identity at the polls in some manner. What's to stop me from going to your polling place and signing Ghost of Stan Parrish (or Jeffy or MIR, etc) and voting?
All I would have to do to vote as someone else would be to glance down at the voter register as I'm waiting in line for the people in front of me. Give them that name. Sign that name. Then I can vote under that name. Now, I'd have to be careful not to pull Ethel or Jenny from the list, but as long as one of the people working at the voting table doesn't know that person, then I'm in the clear. (or go to a different precinct)
Then I can come in again later in the day, when the staffing has changed, and vote as myself, or someone else again.
With an expected turnout of 19% in the primary, it would be highly probable that I could grab a name that won't be used. It would be slightly more difficult in a general election, but as long as I cast my fraudulent vote first, then I have no worries.
If I wanted to crapshoot a little more, I could pay attention to the obituaries in the days leading up to the election. A quick call the the county clerk to verify that "I" had registered would solve that problem.