Lamar Alexander had a nice quip yesterday, for which he's taking plenty of heat; when asked about GOP obstruction of Barack Obama's executive branch nominations, he replied: "That's what nominations are for."
I'm going to defend that -- but only in a limited way. The Constitution gives the Senate a roll in nominations, and it is not only traditional for Senators to use that to influence how executive branch departments and agencies operate, but it is entirely proper. The US system isn't a presidential system, and it isn't a separation of powers system; it's a system of (as Richard Neustadt said) separated institutions sharing powers, which means that the president, Congress, and the courts all have a say in the administrative portions of government (just as the president has a say in writing laws).
It's one thing to seek influence over the way executive agencies work; it's an entirely different thing to attempt to use the nomination process to overturn major laws. It's one thing for single Senators or a handful of Senators to seek to cut a deal over a narrow interest; it's an entirely different thing for the minority party to attempt to implement its legislative agenda by blocking all nominees to a large number of positions. It's one thing to place a hold and negotiate; it's another to filibuster everything.
Oh, and Alexander should give it a rest about how his own nomination for George H.W. Bush's cabinet was held up by Howard Metzenbaum. It's true, but Alexander was blocked (for a relatively short while) because, at least as far as one can tell from a quick Google search, because Metzenbaum suspected financial impropriety. It was personal, not policy-based. Don't forget, by the way, that back then it only required a simple majority for confirmation; even as late as 2001, John Ashcroft was confirmed with 58 votes. It didn't take 60 to be confirmed until January 20, 2009.
So, yes, it's traditional to delay nominations. But what the Republicans are doing now is a complete violation of Senate norms, and a lousy way to run the government. Which is why I think that Harry Reid and Senate Democrats should hit back, hard.