I hear what you are saying but in today's media-saturated world, it is virtually impossible for a public figure like Sarah Palin to do anything in public that is not videotaped or otherwise recorded in some manner. This makes it easy for her critics to pick and choose her more "undignified" moments to show us how unfit she is to hold public office.
Up until the last few decades, it was possible for presidents to appear always dignified for the people. They got to pick and choose when their picture or portrait would be taken and they were dressed to the nines for it. Look at any portrait of George Washington. You think he dressed that way when he did his daily rounds at Mount Vernon?
Their public addresses were carefully scripted ahead of time and because nobody was able to tape it, the newspapers could only print the text that was given to them. What if we had a video of Abraham Lincoln delivering the Gettysburg Address on YouTube? Would we have a different opinion of the Gettysburg Address if we were able to see how it was delivered live in person as opposed to reading it on a slab of marble at the very dignified and stately Lincoln Memorial?
Now George Washington and Abraham Lincoln had their unguarded moments as well. Washington probably spit tobacco juice on the White House floor and Lincoln probably went to fetch the mail in his underwear. But unlike the public figures of today, none of those moments were ever recorded for posterity so it is easy to look back to those years and think of these historical figures as absolutely perfect people who did the dignified thing always.
Now there is a double standard being applied between liberal and conservative public figures. Can you imagine the uproar if President George W. Bush ever emerged from his limousine looking like this?
Washington also had rotten teeth and a fistula in his left cheek caused by an abscess.