Democrats hope to gain effective control of the Senate, which, thanks to its arcane rules, is the main blocker of legislation

IN THE midst of a presidential race, it is easy to forget that political power in America extends beyond the White House. Both candidates have big plans; but they will be unable to implement any of them without Congress’s approval.

Not that Congress has managed to pass everything it wanted since the Democrats took over in 2007. Several initiatives, not least withdrawing from Iraq, have got nowhere. Ask Democratic leaders why, and they say that the party’s narrow majority in the Senate (49-49, with two independents who are allied with the Democrats) has been unable to overcome Republican obstructionism. So, Democrats say, give us more senators, and we will get more done. ...