Romney, in turn, could immediately use the 25th Amendment to install Christie as the new vice president (just as Ford, after becoming president in 1974, named Nelson Rockefeller). President Romney could also name his slate of Cabinet officers, and the Senate could confirm these secretaries in a few days, in keeping with America's honeymoon tradition of deference to an incoming president's Cabinet choices. (The first time in American history that a newly elected president was denied his choice for a Cabinet position was in 1989, when the Senate refused to confirm John Tower to serve as George H.W. Bush's secretary of defense.) It's also useful to remember in thinking about a quick changeover of the executive branch, that most senators are old hands at the confirmation game, and the Senate's staggered election calendar ordinarily ensures that at any given moment at least two-thirds of the body are seasoned veterans.
Of course, if Obama and Biden were willing to do all this in November 2012, they should announce their intentions long in advance, so that their Republican opponents and the voters are not caught by surprise. And they could even cite precedent. Nearly a century ago, President Woodrow Wilson devised a similar plan to approximate British-style transitions. When running for re-election in 1916, Wilson decided that he would resign shortly after the election in the event that he was defeated by Republican Charles Evans Hughes. The plan was for Wilson to name Hughes secretary of state, an office that at the time was first in the line of succession after the vice president. Thus, if both Wilson and his vice president, Thomas Marshall, resigned after Hughes's confirmation, Hughes could take over as acting president long before his formal inauguration in March.
As things actually turned out, Wilson won re-election and nothing came of his early-resignation idea (which was probably just as well, since he did not properly announce his intentions). But if Obama and Biden were to revive Wilson's idea, future incumbents might feel morally bound to follow their precedent, much as presidents after George Washington typically felt obliged to follow his lead of resigning after a maximum of two terms long before the 22nd Amendment required them to do so.
Now turn to House and Senate elections. Here, too, creative resignations could dramatically shorten the current lame-duck period. If every incumbent representative and every senator facing the end of her six-year term were to formally resign the day before the November election, that election could in effect do double duty. First, the election could determine who will serve in the new Congress that will begin service on Jan. 3, as it does now. But it could also operate as a special vacancy-filling election, with the winner entitled to fill out the remainder of the term for the resigning Congress member. Of course, any incumbent who runs for re-election and wins immediately fills the seat she just officially vacated by resignation. But any incumbent who loses would leave early. If we were worried about the very short continuity-in-government gap between resignations and certifications of replacements, then each resignation could be drafted so as to operate conditionally—"effective when my successor's election shall have been certified." (Several recent Supreme Court justices—most recently, Sandra Day O'Connor—have drafted just this sort of conditional resignation, formally effective only upon the appointment of a successor.)
Custom, rather than law, would drive this new system. Formally, losing presidents and vice presidents would be choosing to resign, and incumbent lawmakers would likewise be opting to step down earlier than required by law. But the same is true in Britain—it is longstanding custom that obliged Gordon Brown to step down as soon as it became clear that his political opponents had managed to form a majority coalition. (A legalized alternative would be to move American elections to late December, but this approach leaves little margin for error in the event of an Election Day or Electoral College mishap.)