Lost amid the turmoil of this year's exciting presidential campaign is what's shaping up to be a potentially fascinating congressional cycle.
Here in Maryland, results from the "Potomac primary" provided an early whiff of the changing landscape of congressional elections. Incumbent members of Congress are normally untouchable. But sophisticated challenges mounted by conservative and liberal activists helped unseat, respectively, Eastern Shore Republican Rep. Wayne T. Gilchrest and Prince George's County-based Rep. Democrat Albert R. Wynn.
There is ample evidence - ranging from congressional voting scores to voters' self-description - that the parties are polarizing and becoming more distinct. The Democrats have fewer Southern-based "blue dogs" now than they did when they last controlled Congress, during the first half of President Bill Clinton's first term. And, after 2006, the Republicans have fewer Rust Belt moderates in the tradition of former House Republican leaders Robert H. Michel or Gerald R. Ford.
In that regard, we should not be too surprised that defections from party orthodoxy are potentially lethal, as they were in the case of the two Maryland congressmen punished in the primary for the crime of insufficient partisan loyalty.
Pulling back the focus a bit, the foremost concern for Democrats this November is defending their new majorities. The 2006 cycle was only the second time since 1954 that control of both chambers flipped at the same time: Republicans captured both chambers during the 1994 "Republican revolution" and held those majorities for 12 years.
The challenge facing House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid is whether they can maintain control and build a durable governing majority. Several indicators point to 2008 as a generally favorable congressional cycle for the Democrats.
For one, as is typical in cycles following a change in majority power, a spate of members now relegated to minority status have chosen to retire. So far, about two dozen Republican House members have announced they will not seek re-election this November; defending that many more open seats puts the GOP at a serious disadvantage.
On the Senate side, matters are only a little better for Republicans. Retiring Republican senators in Colorado and New Mexico have given two cousins, Democrats Mark and Tom Udall, a chance to move up from the House to the Senate. Likewise, Republican John W. Warner's pending retirement in Virginia gives former Gov. Mark Warner a great opportunity for another Democratic pickup.
In addition to retirements, congressional fundraising to date this cycle is lopsidedly tilted toward the Democrats.
For all the fuss about lobbyist money in the presidential race, it is in congressional contests that lobbyist money is most significant. At the end of January, the House Democrats' campaign committee had $35.4 million cash on hand to House Republicans' $6.4 million - an almost 6-to-1 ratio. On the Senate side, the Democrats' advantage was a bit more than 2 to 1, $30.5 million to $13.2 million.
Though certain groups, year in and year out, give disproportionately to one party or the other - unions to Democrats, chambers of commerce to Republicans - most non-ideological organizations want their money on the winners. So the Democratic tilt not only confirms that the K Street crowd is betting on the Democrats this year but, unlike the money placed on actual horses at the racetrack, their bets have a self-fulfilling quality because they affect the two parties' competitiveness.
Finally, there is George W. Bush. Ample historical evidence links a president's popularity to his party's congressional performance. When Democrats won former Republican Speaker Dennis Hastert's seat last month in a special election - an Illinois seat held by the GOP for 20 years in a district Mr. Bush carried in 2004 - Republicans around the country shuddered.
A potential silver lining for Republicans is that 2008 cannot be nearly as bad as 2006, because President Bush is leaving office and presumptive presidential nominee John McCain offers his party a chance for a clean slate.
But overall, the spate of retirements and the money advantage probably mean that Speaker Pelosi will pick up roughly a dozen seats in the House, with Senator Reid netting three or four new members for his Senate majority.
Thomas F. Schaller teaches political science at UMBC. His column appears on alternate Wednesdays in The Sun. His e-mail is firstname.lastname@example.org.