And hasn’t been for some time, apparently.  Senator Joe Lieberman had enough standing in his party to win the nomination for VP in 2000.  By 2006, Lieberman had to run as an independent to keep his Senate seat, and while he still caucuses with the Democrats, the independent label fits better.  Lieberman tells Howard Kurtz that the warning signals began almost a decade earlier:

The freshman Democratic senator said he agreed that Congress should formally authorize military action to liberate Kuwait. “I want you to know I’ll strongly support it,” he said, “because I think it’s the right thing to do.”

There was stone-cold silence from the dozen other assembled Democrats—a reaction that Lieberman found “very troubling.”

It was the first step on a winding road that would ultimately produce a bitter breakup between Lieberman and his party. In an age when so much attention is riveted on the brass-knuckle warfare between liberal Democrats and conservative Republicans, perhaps the more corrosive fights occur within each political family, where orthodoxy is strictly enforced.

Of course, we have to get the golly-both-parties-have-gotten-extreme comment, and Kurtz obliges about halfway through his article:

In the end, says Lieberman, “I feel the Democratic Party left me. It was no longer the party it was when I joined it in the image of President Kennedy.” Of course, a similar critique could be offered of the Republican Party, which has veered so sharply right that Jeb Bush said both his father and Ronald Reagan would have had a hard time in today’s party, which “doesn’t allow for disagreement.”

Sorry, but Jeb Bush’s remark was almost satirically foolish from the moment he made it.  Perhaps Kurtz hasn’t noticed, but four of the seven Republican presidential nominees since Reagan left office were named Bush.  The others?  Bob Dole, John McCain, and now Mitt Romney, all of whom few would confuse as an ideologue on the level of Ronald Reagan.  Didn’t Kurtz even bother to apply a little critical thinking to that argument before making it as a counterpoint to Lieberman’s critique?

Everyone knows why Lieberman got ostracized from his party — the war in Iraq.  Practically alone among Democrats, Lieberman stuck to his position from the Clinton era on Iraq and the danger Saddam Hussein posed to the region.  The rest of the party, whose leaders had made public statements warning about the danger of letting Saddam loose when a Democrat was responsible for national security, flip-flopped on the issue when a Republican took over in the White House and suddenly had to make decisions on a global war on terror.  There is nothing illegitimate about a primary challenge (or for principled opposition to the war in Iraq), but Lieberman’s former friends kept mightily silent as the party’s grassroots demonized him as a war-monger who had more loyalty to Israel than the US.  It was a shameful performance, and while Lieberman ended up with the last laugh, it’s no wonder that he has no affection for his former party.

Apart from national-security matters, I don’t agree with Lieberman on much of public policy, but I respect Lieberman for sticking to his principles.  In 2003 and 2004, I thought that had Democrats nominated Lieberman instead of John Kerry to run against George W. Bush, he would have won — and it might not have been a bad outcome, both for the country and for the Democratic Party.