Kim,
From political candidates, I've found that their appreciation of church-state separation is key. If they have that figured out, their religious background isn't so important. Sadly, the Constitution doesn't seem to get much play in political races. If you want some entertainment, look up the Texas republican party platform. No church-state separation there.
Many atheists are libertarians, but that doesn't mean that libertarians are strongly atheist, unfortunately. Atheists also tend to be democrats. Fewer republicans, but they exist. Most atheists I know (even republicans) are aghast at the religious right takeover of that party.
BTW, the ACA is producing a voters' guide for races in Texas. We've posed a number of questions to candidates. We'll be posting results in a week or two. If you live in Texas, you might see how your candidates weigh in.