WASHINGTON – Sonia Sotomayor looks almost certain to emerge from Senate hearings this week poised to become the first Hispanic member of the U.S. Supreme Court.

But political debate over President Barack Obama's plans for the top U.S. court has only begun.

Republicans are ready to resist what they fear could be a sharp leftward turn for the court under Obama's Democratic administration, reversing a steady tack to the right under former Republican President George W. Bush.

For Sotomayor, it is a critical moment to set the public's perception of her. She will define herself for the country in her opening statement, said Doug Kendall, founder of the Constitutional Accountability Center, a liberal legal think tank in Washington.

But for senators, it is much more about stating their case about the future of the Supreme Court itself.

Obama, a former constitutional law professor, chose the 55-year-old Sotomayor to replace the now-retired Justice David Souter, who had been one of four liberals on the deeply divided nine-member court. Members are appointed for life.

A daughter of Puerto Rican parents who grew up in a public housing project in New York, Sotomayor's story of tough beginnings and Ivy League education mirrors Obama's own while her long experience as prosecutor and appeals court judge gives critics few opportunities to attack her credentials.

Democrats appear confident she will get the nod, although not without some difficult questioning.

I suspect she will be confirmed, but I would hope it does not turn into a partisan fight for the good of the courts and the good of the Supreme Court, the Judiciary Committee's Democratic Chairman Patrick Leahy said on the CBS Face the Nation show on Sunday.

FEW CLUES ON POSITIONS

Legal experts parsing Sotomayor's rulings for clues to her positions on everything from abortion to gun control have come up with little, although most agree she will not change the court's ideological balance which has been split with four liberals and five conservatives.

Barring an unforeseen scandal, Republicans also privately concede that Sotomayor will be confirmed -- not least because Democrats control the needed 60 of the Senate's 100 seats to override any minority opposition.

But they hope to use the nationally broadcast hearing to argue that judges should rule according to the law and without regard to personal feeling.

Republicans have made a commitment not to prejudge her. This is her opportunity to explain what some may call troubling or puzzling decisions, one Republican aide said.

Obama entered the argument when he said he favored judges with empathy -- which conservatives portrayed as shorthand for allowing emotion, or bias, to take precedence over statute.

When you show empathy for one party, you necessarily show bias for another group, Senator Jeff Sessions, the ranking Republican on the Judiciary committee, said on CBS on Sunday.

Sessions said Sotomayor's legal record amounted to a philosophical critique of the idea of judicial impartiality, echoing earlier criticisms of her rulings.

Republicans have zeroed in on an early Sotomayor speech in which she said a wise Latina might arrive at better legal decisions than a white man because of her life history.

And questions could also focus on a case in which the Supreme Court, voting 5-4, said the city of New Haven, Connecticut, violated civil rights law by throwing out firefighter exam results which did not produce enough qualified black applicants -- overruling a lower court decision upheld by Sotomayor herself as an appeals judge.

On issue after issue she indicates an advocacy position, Sessions said, although he declined to say if he would actively seek to hold up the nomination.

TREADING CAREFULLY

But many analysts say Republicans must tread carefully through the politics of the nomination.

They have a tricky challenge. They are trying to attack her use of race without impugning her race, and that's not easy to do, said Stephen Wermiel, a constitutional law professor at American University in Washington.

Sotomayor has drawn public support in opinion polls and the top rating from the American Bar Association. She is also seen as a trailblazer by the Hispanic community -- the fastest growing U.S. minority group, accounting for about 15 percent of the population.

There could be questions raised about any judge's ruling on any case. But the fact is, I believe she has a record that is unparalleled, said Democratic Senator Dick Durbin.

Business groups are also holding their fire. The U.S. Chamber of Commerce, the nation's biggest business group with more than 3 million members, plans to withhold any endorsement or opposition until her Senate testimony.

To some extent the timelines are so long and uncertain on what's going to happen in the court that it is underappreciated by Wall Street, said Anne Mathias of Concept Capital Washington Research Group, which tracks Congress for investors.

Manuel Miranda of the Third Branch Conference, a conservative legal group, said Republicans may use the question of the Supreme Court's future to underscore their mounting criticism of the Obama administration on other issues including its huge deficit-spending plans.

The Sotomayor hearings are a spotlight on the president who nominated her, and if the Republicans don't use it that way they are fools, he said.

(Additional reporting by Thomas Ferraro; editing by Mohammad Zargham)

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