Here's my rule of thumb when trying to parse political Twitter feeds: If you see anything snarky or mean, you can bet it's from the politician him- or herself and not a staffer. Not because politicians have some kind of monopoly on snark or meanness, but because professional communications people avoid that tone like the plague. That's why I'm assuming these little digs really are coming from Senator John McCain of Arizona.
Twitter's 140-character limit encourages brevity. That's why you have to be impressed when someone writes tweets that are coherent, complete sentences. Not everything in the Twitter feed of Senator Mel Martinez of Florida is as carefully as those two tweets above, but his feed is definitely better written than most. Of course, this almost certainly indicates that these things are being written by a staffer -- hopefully a Senator doesn't have time to fiddle with sentence structure to make it both well-written and perfectly succinct.
At the other end of the spectrum you have people like Senator Bob Menendez of New Jersey, who embrace Twitter-speak in all its baffling glory, full of abbreviations and intrusive hashtags. It's more efficient in terms of conveying information, but it's still a little unsettling to see a U.S. Senator write "2" for "to" like he's writing out the lyrics to a Prince song. (It's also possible that his office has hired a 14-year-old to serve as Twitterer in chief.)
Some politicians just can't commit to a regular Twitter diet, but can't bring themselves to turn away from it either. Senator Jim Inhofe of Oklahoma did a bit of tweeting just after the 2008 election, then, nearly three years later, jumped back on to endorse Rick Perry for the Republican presidential nomination, only to stay silent for the next three months and counting. Look for him to next offer his opinion on whatever it is everyone in politics will get worked up about in 2015.