Attorney General lacks confidence in his opinion that the bill giving voting representation to DC is constitutional.

John McGinnis talks about Attorney General Eric Holder's "End Run Around the Rule of Law." The article concerns the constitutionality of giving a voting Representative to the District of Columbia. McGinnis sets the issue out very clearly:

It is the long standing practice of the Department of Justice to provide
constitutional analysis of any bill that may be presented to the President so
that the President can fulfill his constitutional duty of signing only bills
that are constitutional. As a result, the Office of Legal Counsel had previous
occasion to conclude that this giving voting representation to the District is
unconstitutional. According to uncontradicted news reports, the Obama
administration’s OLC affirmed the same conclusion.

If the Attorney General believed that this opinion was wrong, he could overrule it. Attorneys General previously have themselves rendered legal opinions. An opinion would provide a measure of accountability because General Holder would have to sign his name to a legal document that purported to show how to get around the Constitution’s clear requirement. Indeed, the Obama administration has argued that increasing the transparency of the legal process within the executive branch will increase respect for the rule of law. What better testament to that transparency than to allow us to compare the reasoning of the Attorney General with that of his own
legal counsel?

Instead, the Attorney General asked the office of Solicitor General at a time when there was no confirmed Solicitor General whether that office would be willing to defend the statute, if passed. The Solicitor General’s office has a long history of defending legislation if there is any credible basis for doing so. But it never opines on the constitutionality of pending legislation, because the question for the President in signing a bill is not whether the legislation might be defended by some argument in Court but whether the legislation is constitutional, not whether some Court might uphold it, but whether the President should give it his own unique constitutional
imprimatur.

If Holder truly believes the statute to be constitutional, he should set out his legal analysis for the world to see. Instead, he hid behind an opinion of the Solicitor General's office that didn't even respond to the correct question. Holder asked the Solicitor's office if it would defend the legislation. The real question is the constitutionality of the statute, not whether there is a colorable argument for constitutionality, the usual standard for defending legislation.

This suggests that Holder lacks confidence in his own position.

A politicized Justice Department.

Edward Whelan says, "Look Who's Politicizing Justice Now" in the Washington Post. Whelan writes

In the course of its usual task of reviewing pending legislation to
identify constitutional problems, OLC determined that the D.C. voting rights
bill, which would give the District of Columbia a voting member in the House of
Representatives, is unconstitutional. The acting head of OLC, David Barron -- a
liberal Harvard law professor appointed by Holder -- signed an opinion setting
forth OLC's conclusion. That conclusion is no surprise, as it has been the
Department of Justice's consistent position, under presidents of both parties,
at least as far back as Attorney General Robert F. Kennedy in 1963 and as
recently as two years ago.

The OLC followed consistent prior findings of the Justice Department that the proposal to give the District of Columbia a voting member in the House is unconstitutional.

The Attorney General overruled that decision. The Attorney General certainly has that authority the Office of Legal Counsel only acts pursuant to delegation of authority from the Attorney General. However, Whelan contends that there is a right way and a wrong way for the Attorney General to overrule the OLC.

Attorney General Eric Holder took the wrong course. "The right way would have been for Holder to conduct a full and careful formal review of the legal question. If that review yielded the conclusion that Holder's position was in fact the best reading of the law -- an extremely unlikely conclusion, in my judgment -- then Holder would sign a written opinion to that effect."

Instead, Holder simply asked the Deputy Solicitor General if his office could defend the statute in court. Since the test of such defense is simply whether a colorable argument exists that can be made without embarrassment, he got the response he wanted. Of course, the Solicitor's office could defend the statute in court.

That was not the proper question to provide a basis for overturning the considered judgment of the OLC that the statute was unconstitutional.