Democrats charged this week that Bill Frist, the Senate majority leader, was manoeuvring to change the rules for approving judicial nominees as a way to shore up his support among conservatives, ahead of a possible run for the White House in 2008.

But Mr Frist's presidential ambitions are not the only ones at play. John McCain and Chuck Hagel, two other Republicans exploring presidential bids, hold key votes in the debate. Taken together, the stances of the three men say a lot about their own politics, and the competing interests at play within the Republican party.