What Would an Obama Presidency Do to the Democratic Party?

If Barack Obama does defeat John McCain this fall, Democrats – who are all but certain to bolster their narrow House and Senate majorities no matter who wins the presidential race – will experience a type of euphoria they haven’t felt in 16 years, when Bill Clinton’s election last gave their party simultaneous control of the White House and Congress.

And surely you remember how that worked out for them. Yes, Mr. Clinton won broad popularity and a second term in 1996, but his presidency brought his party to its weakest point in decades. Democrats were swept out of power in the Senate and House in 1994 and by the time Mr. Clinton left the White House, the G.O.P. seemed to be a permanent majority party on Capitol Hill and in more State Houses than ever before.

There is a political price to owning the White House, and it’s almost always paid by the president’s party, even if the president himself is reasonably popular. Mr. Clinton is the most dramatic illustration of this, but it has been true under presidents of both parties. And it’s something that Democrats, whose November forecasts are growing more bullish by the day, should keep in mind as they begin thinking ahead to the Obama era.

Almost certainly, an Obama presidency will mean that Democrats will take a hit in the 2010 elections, losing Senate and House seats along with some governorships; the question would be how many. If Obama were then to win re-election in 2012, even by a wide margin, it’s doubtful he’d have coattails that would prop up his party’s down-ballot candidates. And under a re-elected President Obama, Democrats would very likely lose more congressional seats and governorships in the “sixth year itch” election of 2014.

With almost no exceptions, this is the pattern that has prevailed in American politics for decades. Only once since 1934 has a first-term president – George W. Bush in 2002, exploiting the country’s extraordinary post-9/11 emotional vulnerability – seen his party gain congressional seats in a mid-term election. Only once since F.D.R. has a second-term president – Bill Clinton, aided by a backlash against the G.O.P.’s push to impeach him over Monica Lewinsky in 1998 – seen his party pick up seats. And since Harry Truman carried 76 House Democrats and nine Senate Democrats to victory in 1948, only L.B.J. in 1964 and Ronald Reagan in 1980 have enjoyed significant coattails as winning presidential candidates.

There are multiple reasons for this. For one, it’s easier for a political party to unite its disparate elements when there is a common enemy – the other party’s guy – in the White House. Plus it’s easier for that opposition party to rally public opinion to its side simply by opposing and undermining an administration’s agenda. Also, Americans seem to like the idea of divided government, or at the very least seem uncomfortable with rewarding a popular president by giving him even more power.

This means that there’s a silver lining in defeat for the party that loses a presidential election. Mr. Clinton’s 1992 triumph is perhaps the definitive example of this. Not only was Mr. Clinton an unpopular president for his first two years, losing significant support even in Democratic-friendly states that had strongly backed him in 1992, but there were also historical forces conspiring against him and his party – specifically a long-overdue partisan realignment in the South stemming from Lyndon Johnson’s embrace of civil rights legislation in the mid’60s.

Years of Republican control of the White House had forestalled significant G.O.P. gains in the South, but Mr. Clinton’s election in 1992 set the stage for a perfect storm in 1994, and the “Republican Revolution” – a gain of 54 House seats and eight Senate seats (and control of both chambers), along with 12 governorships – was the result.

In the same way that George H.W. Bush’s defeat in 1992 was in the long-term interests of the Republican Party, the G.O.P. would unquestionably be rejuvenated by an Obama victory this fall. New congressional leaders would probably emerge and so would a fresh agenda and a new set of prominent voices and faces. Big losers and 2006 and 2008, the party would have an opportunity to begin rebuilding toward Senate and House majorities in 2010.

This hardly means an Obama presidency automatically means a Clinton-esque disaster for the Democratic Party. For one thing, a realignment like the one that was past due in ’94 isn’t on the horizon (and to the extent one is, it favors the Democrats in Rocky Mountain and Western states). Plus, big gains in this fall’s congressional races would give Democrats enough of a pad to absorb modest Republican gains in 2010.

More importantly, the early signs point to a more functional relationship between Mr. Obama and his party’s Capitol Hill leadership than the one that existed between Mr. Clinton and Democratic leaders. And reforms in the House instituted by Republicans have strengthened the Speaker at the expense of once-mighty committee chairmen. Mr. Clinton ultimately calculated that he’d only win re-election by throwing House and Senate Democrats under the bus. This may not be the case for Mr. Obama.

Mr. Obama may prove skillful and popular enough, if he is elected, to maintain his party’s control of Congress throughout his presidency. But he’s still the G.O.P.’s best hope for the foreseeable future of reclaiming their majorities. What Would an Obama Presidency Do to the Democratic Party?