What is it about Sen. Harry Reid’s Senate that makes so many of his members want to leave? Already, Sens. Jay Rockefeller (D-W.Va.) and Tom Harkin (D-Iowa) have announced they are leaving. Neither is in ill health and there are many older members. Both would have a cakewalk in a reelection. And yet more retirements may follow. Keep an eye on Sens. Carl Levin (D-Mich.), Tim Johnson (D-S.D.) and even Dick Durbin (D-Ill.).

Then, of course, John Kerry has decamped for Foggy Bottom and Sen. Robert Menendez (D-N.J.) may find it hard to finish his term. These last two departures mean the Democrats’ margin gets much tighter and the opportunity to ram through progressive legislation diminishes even further.

Sens. Harry Reid (D-Nev.) and Mitch McConnell (R-Ky.)- Alex Wong/Getty Images

Pols who come to Washington to “make a difference” — which for liberals means passing legislation — must find Reid’s Senate deadly dull. Rarely do votes get taken. There hasn’t been a budget in over three years. Reid is likely either to whittle down antigun legislation to the bare bones or block it entirely. The president looks anxious to scuttle immigration reform before it starts. In short, Democratic senators do very little. (How they get reelected doing so little is beyond me.)

At least Republicans see their mission as playing defense 24/7. Stay alert. Don’t let more damage be done. Think how to minimize the debt. It’s not grand, but it is challenging and invigorating in a way. Democrats, on the other hand, have to be content to do nothing.

So it is a wonder more Democrats don’t leave. This year Virginia has a gubernatorial race that Sen. Mark Warner (D-Va.) could win in a heartbeat. In 2014 gubernatorial races abound. Democrats will be term-limited out in Massachusetts, Arkansas and Maryland. There will be competitive races against potentially vulnerable GOP incumbents in states such as Florida, Maine and Pennsylvania.

I suspect many more Democrats will consider retirement or opt for gubernatorial races in the next few years. Anyway, the sixth year of an incumbent president’s term is not hospitable grounds for members of his party in the House and Senate. So why raise millions, work furiously and get, if you “win,” more time to twiddle your thumbs? It might not sound like a bad life to you and me, but for those motivated by power and ego it is necessary to occupy a position where you can shine. No Democrats shine in Harry Reid’s Senate. They stall. They duck. They evade. But they don’t accomplish anything. For the ambitious among them, the Senate is no place to be.

Jennifer Rubin writes the Right Turn blog for The Post, offering reported opinion from a conservative perspective.