A long road to travel: Barack Obama’s unchecked legislative ambitions lead supporters to worry most about his prospects for slipping up

Celebrity watchers think of him as the best-selling face since Princess Diana. Conservatives call him the Apologiser-in-Chief. Supporters and detractors alike sometimes see him as a lucky figure – a view reinforced by Arlen Specter’s defection on Tuesday, which opens up a potentially impregnable Democratic majority in the Senate.