Easy answer to your question: get preapproved NOW, as opposed to later. Rates may go up, or not, once the election outlook and fiscal cliff near, but preapproval is just the start of the loan process and is not rate dependant. You won’t be locking the rate on your loan until you have a contract and closing date, so there’s a (sometimes lengthy) time frame between getting preapproval and locking your rate.
Also, make sure you’re preapproved, not just pre-qualified. Your lender should examine your credit, calculate your debt to income ratios, and look at your income and asset statements. Just pulling a credit score does not mean you’re preapproved!
Bottom line, if you are preapproved, you have the freedom to shop for homes, no matter where rates are at. If you wait and rates drop dramatically, you’ll be behind the crowd of buyers who had preapproval letters in hand and were ready to jump when they found the home they wanted to write a contract on.