Supreme Court nominee Elena Kagan had functioned as a "political operative" in her governmental work, the Senate's top Republican charged Wednesday.

Senate Minority Leader Mitch McConnell (Ky.) asserted that Kagan's work for Presidents Bill Clinton and Barack Obama had taken on a distinctly political bent that called into question her ability to serve on the Supreme Court.

"The more we learn about Ms. Kagan’s work as a political advisor and political operative, the more questions arise about her ability to make the necessary transition from politics to neutral arbiter," McConnell said in a speech on the Senate floor. "As Ms. Kagan herself once noted, during her years in the Clinton administration, she spent 'most' of her time NOT serving 'as an attorney' but as a policy advisor."

An aide to the GOP leader described McConnell's speech as a "new front in the case against Kagan," the solicitor general for whom nomination hearings are set to begin before the Senate Judiciary Committee next week.

Kagan is still seen as likely to win enough support from senators in both parties to win confirmation, though McConnell and Sen. Jeff Sessions (R-Ala.), the ranking member of the Judiciary committee, have expressed reservations about Kagan's ideological track record.

McConnell said he lacked confidence in her ability to parse out politics and legal judgment.

"So the question before the Senate is whether, given Ms. Kagan’s background as a political advisor and academic, we believe she could impartially apply the law to groups with which she doesn’t agree and for which she and the Obama administration might not empathize," he said. "So far, I don’t have that confidence."

UPDATE: The White House is pushing back against McConnell's statements, pointing out that Kagan often urged her administration colleagues to avoid politicizing legal issues.

Kagan, for example, once cautioned against changes to a campaign finance bill out of fear that "active support of such an amendment by the President will look like a politically driven effort to dilute the McCain-Feingold bill."

White House spokesman Ben LaBolt said McConnell's comments were a sign of desperation:

“As the hearings approach, Republicans are getting increasingly desperate, relying on scribbled notes in the margins of documents and ignoring the actual advice Kagan offered in an attempt to distort her views.  As a staff lawyer and policy advisor to President Clinton, Elena Kagan provided the President with legal and policy options that reflected the President’s well-established views.  Senator McConnell knows that the documents should not be interpreted as a reflection of her views, as he made clear that documents from Chief Justice Roberts’ service in the Reagan and Bush administrations reflected advocacy requested by Roberts’ bosses and that views expressed in those documents represented ‘that of his client.’  Elena Kagan agrees with Chief Justice Roberts that judges confront issues differently than staff attorneys for an administration with a position.”