One would have to be a complete idiot to take at face value anything in a politcal ad run on TV. Of course, we have a complete idiot in the White House now, who was voted in twice, so there obviously must be quite a few morons in this country.
Most of the negative claims made about candidates in these ads are at best misleading, and often just plain lies. So, if you would like not to vote as a complete idiot, there is a great, non-partisan web site called Factcheck.org. They check the veracity of claims made in ads or speeches by candidates of both parties, and identify the bullshit.
The down side of Factcheck is that you will quickly realize that both sides are completely full of shit......but then, they wouldn't be running for office it they weren't!