Max Baucus' surprise retirement on Tuesday furthers a growing trend of longtime Senators heading for the exits over the past few years and affirms a simple reality: The Senate just isn't a very fun place to be these days.

"When old bulls are retiring even though their party is in the majority -- that says a lot about how dysfunctional the Senate has become," said Republican pollster Glen Bolger.

Baucus is the ninth senator to either resign or retire in advance of the 2014 election and the 27th Senator to retire from the chamber over the past three election cycles (2010, 2012 and 2014.) That's the highest number of Senate retirements over a six-year period in more than four decades, according to the indispensable Aaron Blake, and we still have a long way to go in the 2014 election.

And, it's not just the number of retirements, it's the people retiring (and the institutional wisdom they possess) that make the trend so intriguing. Baucus, Sen. Carl Levin (D-Mich.) and Sen. Jay Rockefeller (D-W. Va.) -- all of whom are retiring in 2014 -- will have served more than 100 years between them when they retire next November. Of the six committee chairmen up for re-election in 2014, five of them are retiring -- with Louisiana's Mary Landrieu as the lone exception.

Six years ago, 44 senators had served at least three terms; today that number is 32. At the start of the 113th Congress, more than half of the senators had served one full term or less. That's absolutely remarkable.

The Senate is simply a very different place than it was even a decade ago. And, judging from the number of incumbents heading for the exits, it's quite clear that they believe is it a lesser place.

Maine Republican Sen. Olympia Snowe, who retired in 2012 despite facing no real opposition for a fourth term, acknowledged that changed reality bluntly in an op-ed for The Post roughly a year ago. “The Senate is not living up to what the Founding Fathers envisioned,” she wrote.

It's hard to argue that the Senate has become more like the House -- more party-line voting, less across-the-aisle legislating and a devolving emphasis on personal relationships.  "As Washington has become more polarized, so has the Senate, which has soiled its fabric and unique nature," said Penny Lee, a former top aide to Senate Majority Harry Reid and now a Democratic lobbyist.

What is less clear is why the Senate has changed -- and who's responsible.

Republicans place the blame on Senate Majority Harry Reid. "Reid has basically eliminated the committee process in the Senate," argued one senior Republican Senate aide. "The bill on the floor this week is a perfect example and may actually have been the tipping point with Baucus.  It’s a Finance Committee bill that never went through the committee, the chairman is opposed to it, and they may not even let him offer an amendment."

Democrats, on the other hand, believe the emergence of a outspoken conservative wing within the Senate -- led by the likes of Rand Paul of Kentucky and Ted Cruz  -- have made the chamber a less pleasant place to be and a more perilous one for Republicans willing to work across the aisle.

The primary defeats of Sens. Richard Lugar (R-Ind.), Bob Bennett (R-Utah) and Lisa Murkowski (R-Alaska) over the past few elections suggest the political pitfalls for Republicans perceived as not adhering strictly enough to core principles.

It's worth noting, of course, that distaste for the current state of the Senate isn't the only factor in these retirement decisions.  Age matters: Baucus is 71 years old, Levin is 78 and Rockefeller is 75.  So, do personal circumstances that are, by their nature, unique to each Senator. (Baucus told the Associated Press Tuesday: "I don't want to die here with my boots on. There is life beyond Congress.")

But, the totality of retirements in the Senate over the past three elections suggest something broader is happening.

"These old timers have spent the last six years suffering through the frustrating parts of job – voting into the night on nonsense, partisan bickering, glacial progress on key issues – without the pay-off of being able to get their hobby horses to pass or attached to some omnibus bill," said Ed Goeas, a Republican pollster. "Now, they’ve had enough and are ready to move on."