re: Not yet.
You forget Mary Anne that the Senate is a terrible place to gain prestige for a presidential run. It's actually considered a liability because the longer your voting record the more of a target it becomes.
We have a first term governor with no national governing experience who's name has been bounced around as a possible presidential candidate.
The American voters are a fickle bunch. I'm not sure any logic applies when it comes to who will make a viable candidate and who won't.
If your contention was merely expressing your own druthers that any candidate get national experience first then I wholeheartedly concur. Unfortunately, I rarely vote for winners anymore. It's a bit disheartening.
Art