Congress's Responsibility for President's Court Nominees

The Washington Post has an interesting editorial about replacing Souter. Most of it praises the outgoing justice's intellectual ability and open-mindedness and urges a simliarly qualified replacement. But the last paragraph touches on an important question about Congress's responsibility in the confirmation of the President's Supreme Court nominees. Just how much deference should it provide to the President's choice? Since the constitution provides little guidance, how much is the "mainstream" of thought used as a standard?

"The temptation for Republicans will be to treat Mr. Obama's pick as some Democrats -- including, sad to say, then-Sen. Obama -- treated President George W. Bush's. It is legitimate for senators to take a nominee's ideology into account and to probe it within ethical limits, but it is also important to keep in mind that elections have consequences, and that the president is, as a general matter, entitled to name justices who reflect his own understanding of the Constitution and the role of the courts. We say this having supported Mr. Bush's two nominees -- Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr. -- as within the mainstream of conservative legal thought."