Last week, Pennsylvania Sen. Arlen Specter was one of the most liberal Republicans in the Senate. Today, he's the most conservative Democrat. Specter has said he will retain his independence, which would mean he's not necessarily the filibuster-breaking godsend the Democrats hope. Still, historical evidence argues that Specter is poised for a leftward veer that will be terrific news for President Barack Obama.
Specter has been a genuine moderate, with ratings hovering around the 40 to 60 percent range from conservative and liberal groups. He has often voted for free trade, tax cuts and spending restraint. He also voiced opposition to the pro-union "card-check" legislation, and his support of Obama's "cap-and-trade" environmental effort is doubtful given the strength of Pennsylvania's coal industry. If he continues that record, he won't be a solid Obama supporter.
But party-switchers often change their votes as well as their labels.
The day after Republicans won control of the Senate in 1994, Sen. Richard Shelby of Alabama switched to the Republican Party. He had been a relatively conservative Democrat and had high-profile conflicts with President Bill Clinton, so the switch wasn't a great surprise. But observers might be surprised to look back at what happened to Shelby's voting record. According to the American Conservative Union, for eight years Shelby's conservative voting percentage had ranged between 43 and 76. Even in 1994, as Shelby often found himself opposing the Clinton administration, the ACU gave him only a 55. But from 1995 to 2000, his ACU rating only once dipped below 90, and he scored a perfectly conservative 100 in 2000 and 2001 (even though Citizens Against Government Waste dubbed him the "King of Pork"). Meanwhile, the liberal Americans for Democratic Action had rated the Democratic Shelby 35 percent liberal in most years. As a Republican, however, ADA rarely found him more than 10 percent liberal. Shelby's voting clearly changed when his party label did.
A few months after Shelby, Colorado Sen. Ben Nighthorse Campbell also switched from Democrat to Republican. He underwent a similar ideological migration. ACU rated him 12 and 25 in his first two years as a Democrat in the Senate, then 96 in the year of his switch. After that, his conservative score ranged from 72 to 96 until his retirement in 2005. His ADA score fell almost like stair steps — to 55 from 75 percent liberal in 1993 to an unusually low 30 the year he switched, then 45, 25, 25, 15, 5. According to Michael Barone, co-author of The Almanac of American Politics, Campbell switched his stands on partial-birth abortion, oil drilling in Alaska and assault weapons.
In 2001, Sen. Jim Jeffords of Vermont left the Republican Party and became an independent. Conservatives said he was actually voting like a liberal Democrat. But that wasn't quite right. Since he entered the Senate in 1989, his average ACU rating had been 27 — definitely the most liberal Republican, but not Ted Kennedy country. His ADA average was 58 — liberal for a Republican, but a long way from Vermont Democrat Pat Leahy. After the switch, Jeffords' ACU rating started falling like GOP approval ratings: from 40 in 1999 to 29 in the year of the switch to 6, 10, 4, 8 and 4 during the rest of his tenure. He and Leahy became twins.
Why do senators vote differently when they change parties? First, the pressures from the party caucus obviously change. Surrounded by new colleagues, pressured to help the party deliver on its promises, the new guy finds himself going along with his new team. Of course, the real point here may be that the party-switcher has been liberated from the pressures in his former caucus that kept him from voting as he would have preferred.
Second, when an elected official switches parties in Washington, he also switches constituencies back home. Campbell's political challenge as a Democrat was to persuade some 60 percent of the voters of Colorado, ranging from center to left, to support him. As a Republican, his goal became to get some 60 percent of Coloradans ranging from center to right to back him.
Specter will face similar pressures, in Washington and Pennsylvania — and he'll also be free of the pressures of the Republican caucus. There's every reason to expect his voting record to shift left.