On the cards is an anticipated grilling on the deeply divisive issue of limits on the power of the US presidency.
Barring any unexpected revelations during several days of testimony this week, Alito was expected to be confirmed by the Senate Judiciary Committee to replace retiring Justice Sandra Day O'Connor when it votes on the nomination next week.
But this week's Senate interrogation seemed certain to underscore the bitter partisan divide in Congress, as legislators question the 55-year old jurist on his views on a wide range of divisive topics, including his views on civil rights, abortion, and the constitutional limits of the presidency - one of the most heated issues on Capitol Hill in recent years.
"This hearing comes at a time of great national concern about the balance between civil rights and the president's national security authority," said the committee's Republican chairman Arlen Specter, as the hearing got under way on Monday.
The panel's top Democrat, Patrick Leahy, was even more pointed.
"The challenge for Judge Alito in the course of these hearings is to demonstrate that he's going to protect the rights and liberties of all Americans and, in doing that, serve as an effective check on government overreaching," Leahy said.
"No president should be allowed to pack the courts - especially the Supreme Court - with nominees selected to enshrine presidential claims of government power," Leahy added.
Alito (L) is expected to be grilled
by liberal senators on abortion
The issue of presidential power has come into the spotlight following recent revelations of a controversial secret domestic spying programme initiated by Bush after the 11 September 2001 terror attacks, which critics say violates the US Constitution.
Tough questioning was also expected on Alito's views on abortion - a perennial flashpoint in US politics. Justice O'Connor, a centrist and a key Supreme Court swing vote, supported abortion rights for women from the bench, further increasing passions over the proper qualifications for the person chosen to replace her.
A staunch conservative, Alito is seen by abortion rights advocates as likely to cast a vote to overturn the landmark Roe v Wade ruling which legalised the procedure some three decades ago.
Alito currently serves as a federal appeals court judge in Philadephia, Pennsylvania, and has frequently taken judicial positions seen as being at odds with abortion rights.