Mr. Lugar, ranking Republican on the Foreign Relations Committee and a longtime leader on controlling nuclear proliferation, is a sober and genial fellow. He is a conservative, always has been. He is experiencing a challenge from the right. He’s been under fire, for instance, for voting for the confirmation of Justices Sonia Sotomayor and Elena Kagan. As a matter of form, policy and tradition he did the right thing. He also helped shepherd through the nomination of John Roberts as chief Justice. He did the right thing there, too. He firmly backed President Bush on Iraq until he came to have doubts about administration policy and execution, and when he’d thought it through he took to the floor of the senate to explain his thinking, and his break.