The part where Karl Rove, writing in today's Wall Street Journal (subs. req'd; alt. free link) as a former (sic) adviser to George Bush --
A party that wins control by that narrow margin can quickly see its fortunes reversed when it fails to act responsibly, fails to fulfill its promises, and fails to lead.
But since it's Rove peddling White House talking points, what he means is not George Bush's 540 vote victory in winning the presidency in 2000, (or 1 vote, if you count the Supreme Court margin), but --
The Democratic victory in 2006 was narrow. They won the House by 85,961 votes out of over 80 million cast and the Senate by a mere 3,562 out of over 62 million cast.
The main obstacle to the Democrats achieving anything since 2006 has been a constitutional system that leaves Rove's boss in the chief executive position long after his public support has collapsed.