Misstated?

What is up lately with all of these politicians using the term misstated or misspoke?  Why don't they either stick to their beliefs (Akin) or say they lied (Ryan) about what they said.

A few weeks ago you may remember Rep. Todd Akin made some incorrect comments about how if a woman is legitimately raped the body has ways of fending off pregnancy.  After lots of pressure from media, various groups, and even fellow politicians he took it back and said he misspoke. Why didn't he stick with what he believed in?  or say that he was wrong and will be doing further research on the topic?  When he said he misspoke it makes it seem like that is not what he meant to say or he stumbled over what was on the teleprompter.

The newest addition to the list is VP canidate Ryan.  In an interview he said that he ran a marathon in under 3 hours (under 7 minutes a mile).  After several questions arose he eventually said he misstated the time and it should have been closer to 4 hours.  How do you just lose an hour in a marathon?  Did he think someone would say that 4 hours is way to long of time to run a marathon?

So who is the next political person that is going to use this excuse as a scapegoat?  No, you can't say VP Biden because even President Obama would admit that he was mistake.