Rudy Giuliani has recorded a fear-mongering robocall for the McCain-Palin campaign that distorts Senator Barack Obama’s stance on mandatory sentences for society’s worst criminals.  Obama opposes mandatory minimum sentences for some offenses, arguing:

We have a system that locks away too many young, first-time,
non-violent offenders for the better part of their lives – a decision
that’s made not by a judge in a courtroom, but all to often by
politicians in Washington and state capitals around the country.

But Giuliani’s robocall drops the, rather important, word "minimum," making it seem that Obama opposes mandatory sentences in general:

Hi, this is Rudy Giuliani and I’m calling for John McCain and the
Republican National Committee, because you need to know that Barack
Obama opposes mandatory prison sentences for sex offenders, drug
dealers, and murderers. It’s true, I read Obama’s words myself. And
recently, Congressional liberals introduced a bill to eliminate
mandatory prison sentences for violent criminals — trying to give
liberal judges the power to decide whether criminals are sent to jail
or set free. With priorities like these, we just can’t trust the
inexperience and judgment of Barack Obama and his liberal allies. This
call was paid for by the Republican National Committee and McCain-Palin
2008.

HuffingtonPost.com notes that Obama’s stance against mandatory minimum sentences is bolstered by several studies of criminal behavior
which show that "mandatory minimum sentences are less effective than
discretionary sentencing and drug treatment in reducing drug-related
crime."

TalkingPointsMemo.com has an audio recording of the call.