The intraparty struggle within the Democratic Party over what exactly to do with Arlen Specter now seems to have been worked out. For the time being, at least, Specter will not get to keep his overall seniority (which was apparently promised him by Majority Leader Harry Reid), but as a consolation prize will chair the Crime and Drugs Subcommittee, part of the Judiciary Committee Specter used to chair as a Republican. This struggle may wind up being re-fought after the 2010 election, but for the next year and a half the dust appears to have settled on the issue.

These problems always arise at the edges of party membership. But it is telling that Specter is being treated a bit differently than the last time Democrats had to deal with a similar issue -- with Joe Lieberman. The two situations aren't exactly the same, which may explain why the outcome was different for the two, though.

But before we get to Lieberman, a quick review of the past week or so is in order first. After Specter announced he was jumping ship, he has not exactly been what you could call "a loyal Democrat" by any stretch of the imagination. But then, that's what he promised he would do when he made his announcement, so the fact that he voted against two major pieces of legislation which President Obama wanted can be seen as "what was advertised." Specter never said he'd be a faithful, party-line voter, after all -- in fact, he said almost the opposite and proclaimed he would be an independent vote and not a 60th Democratic senator voting in lockstep with the president.

That was all fine and good, but then Specter made two egregious errors. The first came over the weekend, while being interviewed on "Meet The Press," when Specter responded to being asked if he was promised his years as a Republican would be counted for seniority purposes in his new party. His answer was a bit regal: "That's an entitlement. I've earned the seniority. I will be treated by the Democrats as if I'd been elected as a Democrat."

This was, in fact, the deal that Harry Reid had agreed to: count Specter's 29 years as a Republican senator as if he'd been a Democrat all along.

The only fly in this particular ointment was that that's a lot of seniority. And this would vault Specter almost to the front of the line when it came to hand out committee assignments -- in front of a whole lot of very senior Democrats who weren't exactly thrilled about being bumped down a notch. Which is why seniority is so important in Congress. But, in the normal course of things, this issue wouldn't have normally come to a head until after the 2010 elections. Because committees are only shuffled at the beginning of a congressional term, which just happened at the beginning of this year when the new congressional class was sworn in. So it wasn't like Specter's seniority would have really meant anything for the next few years anyway, and the real decision would have been up to the incoming Senate Democrats in 2011.

But Reid apparently didn't count on the pushback from within his own caucus. Because on Tuesday night, the Senate voted to strip Specter of all his seniority, leaving him as the freshest of freshman Democrats in the Senate (he'll be second from the bottom when Al Franken is seated).

This was due mostly to Specter's statement to the New York Times that he hoped Minnesota "justice" prevailed so that Franken's Republican opponent Norm Coleman would eventually be seated. This was the straw that snapped the Democrats' loyalty to anything their (nominal) leader Harry Reid had promised Specter, and they promptly stripped Specter of his 29 years seniority as a result.

Today it was announced that Reid had worked a backroom deal out, shuffling a few people around, giving Dick Durbin a subcommittee on human rights in exchange for Durbin's stepping aside and letting Specter chair the crime and drugs subcommittee. It was a face-saving measure, not only for Specter, but also for Reid as well (who, throughout the entire episode, looked weak and out of control of his own party's caucus).

But comparisons to Lieberman aren't entirely correct, for two reasons. Lieberman votes with Democrats extremely reliably, except on the Iraq War. And Lieberman could have switched parties and become a Republican, if he chose to. It was a real threat, in other words. Specter, by just having jumped ship himself, really doesn't credibly have that threat to make, since Republicans (at this point) probably wouldn't even let him back in the party. Plus, if Specter somehow did manage to switch back to the GOP, he'd still be facing the same primary challenger he switched to avoid in the first place.

Lieberman's sins, to the Democratic Party faithful, were a lot more severe than Specter's. Lieberman didn't just casually mention one Senate race he wanted a Republican to win, he actively campaigned so hard for John McCain in the 2008 election everyone thought they were joined at the hip -- which culminated in Lieberman being on McCain's short list for veep, and Lieberman addressing the Republican National Convention. On the Iraq War, Lieberman voted consistently with Republicans. Since he lost his Democratic primary, Lieberman ran and won as an independent. In other words, there was a lot more justification for stripping Lieberman of his seniority than Specter's sins over the past week.

But Specter is painted into a corner now. He can't go back to the Republicans, and he really doesn't want to face a strong primary challenger next year from a more "Democratic" Democrat. That's why he switched in the first place -- to save his own political hide. He has to convince not only Pennsylvania voters at large to support him in his general election, but he now also has to convince Pennsylvania Democrats to nominate him in the first place. And a fairly strong candidate, two-term Democratic House member Joe Sestak, is publicly speculating about whether he will challenge Specter next year. So the Democratic nomination is not going to be a shoo-in for Specter anymore (which, ironically, was the other thing Reid all but promised Specter to convince him to make the switch).

Although I am a bit dubious about the political wisdom of stripping Specter's largely-meaningless seniority right now (as opposed to after the 2010 election, when it should have happened, if it was going to), I do think that a Democratic primary challenger is a good thing for Pennsylvania, a good thing for the Democratic Party, and a good thing for politics in general. Senators should not see their re-election as something they are "entitled" to, just because some party pol made them a promise.

Because with a challenge from within Specter's own new-found party in the primary, he's going to have to pay a lot more attention to what Democrats in Pennsylvania want him to do. He's going to have to actively work for their support. Which means he will think twice about voting with Republicans from here on out. He still likely will buck his party and his party's president in the next year and half, but I'd be willing to bet that he's going to do it a whole lot less than he would have if Reid's promises had actually held up. If Sestak does challenge Specter, then Specter is going to have to keep his eyes on Democratic primary voters before he thinks about general election voters -- which will also have the effect of making him think twice (and maybe even three times) about voting against his new party.

And that's the way it should work. While -- as I said -- I question the political tactic of stripping Specter of his seniority at this point in time, such seniority is most decidedly not an "entitlement" for an aisle-jumper. And, Senator Specter, neither is getting re-elected. To earn that, you have to answer to the voters for what you say and how you vote. So consider the past week a warning shot across your bow, and reflect on it every time Republicans call for a cloture vote in the next year and a half. Because if you truly do want to save your political skin, you're going to have to woo some Democratic Pennsylvania voters in the meantime.

-- Chris Weigant