Most political prognosticators forecast that Republicans will recapture the U.S. Senate in this fall's midterm elections. The GOP already holds the House, and the fact that Republicans control the lower chamber but not the upper one is actually something of a puzzle and an historical anomaly.
First, the history: Republican Speaker John Boehner has now presided over a Republican House majority for two terms without a companion Senate Republicans majority. When was that last time the GOP controlled the House for two consecutive Congresses — four years — without controlling the Senate?
Never: Not once in the party's history, dating all the way back to its 1854 founding. On the other hand, the Republicans held the Senate but not the House during the first six years of the Reagan Administration.
As I explain in "The Stronghold," my forthcoming book from Yale University Press, Republicans have been a stronger presence in the Senate in the past half century party because more of the small-population states lean Republican. Therefore, the GOP has consistently held a higher share of Senate seats than the population contained in the states the party's senators represent.
For example, during that six-year Senate Republican majority between 1981 and 1987, the GOP averaged 54 seats out of 100 but represented an average of 49 percent of Americans. During the 12-year GOP majority era from 1995 to 2007 the Republicans' seat-to-population inflation averaged six points.
The extreme case of the GOP's small-state advantage came at the start of the 107th Congress of 2001-2002. Despite representing just 42 percent of Americans, the 50 Republican senators had a working majority thanks to the tiebreaking vote of Vice President Dick Cheney, who fittingly hails from Wyoming, America's least-populous state. (Vermont Republican James Jeffords' party switch in April 2001 shifted Senate control to the Democrats.)
Now, the puzzle: Given their built-in small state advantage, why do Republicans presently control the House but not the Senate? Shouldn't it be the inverse?
The short answer, of course, is gerrymandering. Thanks to a strong 2010 election cycle in which the GOP posted significant gubernatorial and state legislative wins, Republican state leaders were able to draw favorable U.S. House lines in many states. (Solidly Democratic Maryland was an exception.)
The GOP's gerrymandering advantage was evident in the 2012 presidential results. President Barack Obama beat Mitt Romney in 26 of 50 states and by 2.8 percent in the national popular vote — thin majority margins, sure, but larger than the 47.6 percent share of House districts Mr. Obama carried (207 of 435) because Republicans successfully packed Democratic voters into fewer districts in order to help elect more Republicans to the House.
Nor was it a surprise when, after the 2012 election, some Republicans in Ohio, Pennsylvania and Virginia attempted to have their states adopt the Maine/Nebraska method of apportioning presidential electors. In those two states, presidential candidates amass one elector for every U.S House district they carry, and two electors if they win the statewide popular vote.
If that method were applied retroactively to all 50 states in 2012, Mr. Obama would have collected 262 electors — 207 for the House districts he won, 52 for the 26 states he carried, plus three for the District of Columbia. Despite receiving 3.5 million fewer votes, Mr. Romney would have won.
That's hypothetical. The reality is that Republicans still control only the House. Because the electorate tends to be older, whiter and more affluent in midterm cycles than presidential cycles, after blowing chances in 2010 and 2012 to recapture the Senate, the GOP may finally add the upper chamber to its House majority this year. With Republicans almost certain to flip Democratic-held seats in Montana, South Dakota and West Virginia, plus favored Republican candidates in Arkansas and Louisiana, Fivethirtyeight.com's Nate Silver puts the GOP's chances of flipping the Senate at 60 percent.
Republicans continue to struggle in presidential elections, however, which may explain the efforts to sue or impeach President Obama. (Or just re-re-re-re-investigate Benghazi.) But that's a topic for another day.
The bottom line? The GOP is a strong House party and a weak presidential party, with the Senate yet again up for grabs.
Thomas F. Schaller teaches political science at UMBC. His column appears every other Wednesday. His email is email@example.com. Twitter: @schaller67.To respond to this commentary, send an email to firstname.lastname@example.org. Please include your name and contact information.