One of the interesting things about recent elections is that Republicans have tended to do better the farther you go down the ballot.
They've lost the presidency twice in a row, and in four of the last six contests. They've failed to win a majority in the U.S. Senate, something they accomplished in five election cycles between 1994 and 2006.
But they have won control of the House of Representatives in the last two elections, and in eight of the last 10 cycles.
And they've been doing better in elections to state legislatures than at any time since the 1920s.
One reason for this is that, as I have written, Democratic voters are clustered in large metropolitan areas, which helps them in the Electoral College but hurts in legislatures with equal-population districts.
But there's another reason, which has been particularly glaring in races for the U.S. Senate: candidate quality.
Over the years, I've noticed that Democrats tend to have a disproportionate share of candidates with sharp political instincts and ambition.
Probably that's natural. Democrats tend to want more government, and smart Democrats like to go into politics. Smart Republicans tend to take other paths.
This helped Democrats maintain congressional majorities and big margins in state legislatures when Republicans were sweeping five of six presidential elections from 1968 to 1988.
They lost that edge in candidate quality in the 1990s, but they seemed to regain it in the later Bush years.
That's the main reason why Democrats have a 55-45 majority in the Senate after the very Republican election cycle of 2010 and a 2012 cycle in which 23 Democratic and only 10 Republican seats were up for grabs.
It's generally agreed that Republicans booted sure Senate wins in 2010 in Nevada and Delaware and perhaps Colorado.
Foolish statements about abortion and rape cost Republicans wins in Indiana and Missouri in 2012. They also lost two very winnable races in North Dakota and Montana and two races in which former officeholders fell just short in Wisconsin and Virginia.
Last month, Karl Rove said his Crossroads group would spend money in primaries to prevent the nomination of weak candidates.
He was promptly attacked by L. Brent Bozell of the Media Research Center, who said conservatives, not the Republican establishment, should choose party nominees.
Actually, both insiders and outsiders have made bad picks. Rove can cite the Senate races listed above.