If you spilt the list of Democratic Senators into 3 or 4 groups based on seniority, the oldest group would be the most liberal overall. Many of the more recent Senator, from traditionally red or purple states are far less liberal or progressive. But, you need to look at the Senators currently on the committee.
Commerce is the committee where this might happen - look at this list - look at the members, ignoring Inoye, who really is the most senior and who gave up the chair, only Lautenberg in the second half is liberal or progressive. Then look and see the bottom of the first half - Pryor, Klouchar, and Warner are also more conservative that the more senior members. (I can't really place where Cantwell is.) Not having any ideas of the personal relationships, this is a committee where they could move to the right if anyone challenges.
The Judiciary committee is headed by arguably the most liberal member - Leahy. Could he be challenged? Looking at the current list, they look sufficeintly liberal that he wouldn't, but an ambitious Senator more to the center could initiate a "coup".
Another possibility of a rightward "coup", is Armed Services, where Levin has questioned things like torture. Look at the members, their median is to right of the entire caucus and Levin is to left. *Again, I have no insight to personal relationships.)
Look at who is currently in Finance - Baucus, Rockefeller, Conrad, Bingaman, Kerry, Lincoln, Wyden, Schumer, Stabenow, Cantwell, Nelson(fl), Menendez, Carper. My guess is this would likely come down to Schumer vs Baucus, if Schumer does not become Majority leader, but this analysis works if you take any of the more progressive members. (logic Conrad is too close politically to challenge Baucus, Kerry would likely prefer to keep SFRC, where I doubt he would be challenged, Rockefeller would likely prefer to fight to retain Commerce.) I don't see any of the others being sufficient power players at this time. This is the committee that will vote in late 2010. Baucus is likely to have himself, Conrad, Lincoln, Nelson and Carper. He also is supposed to be a very good friend of Rockefeller, who could be the needed 6th vote. I would guess Baucus is safe.
Now, Budget there is far more of a chance for change - here is a list of members -
http://budget.senate.gov/democratic/democrats.htmlOn SFRC, there is no one with Kerry's stature, and his committee's hearings have been extremely well planned, covering a broad range of issues. Their tone has shown more respect to all Senators on the committee than was shown even under Lugar - who was much better on that than Biden. Here is that committee -
http://foreign.senate.gov/ (Dodd will be gone in 2011, leaving only Feingold and Boxer having any significant time on this committee.) (I suspect that had leadership been voted on for years before, Kerry would likely have been voted to head the committee in 2004.)
On HELP, I agree with the article's assessment, it is not clear that anyone would challenge Harkin -
http://help.senate.gov/Doing this, I see that it might come down to personal relationships. If a person is doing their homework and running the committee well, I suspect that there will be a feeling, given the tradition, that removing him/her will be a humiliation. Now it is done behind the scenes when the Senator or the leadership think that the job is too much for them - and that is subjective. No one in the HELP committee would have moved against Kennedy in Nov 2008.