"The filibuster's on the table," Democratic Sen. Barbara Boxer of California said as Alito headed back to Capitol Hill on Tuesday. Alito is courting Republicans crucial to his attempt to replace retiring Justice Sandra Day O'Connor.
But the No. 2 Senate Democrat urged restraint. "I don't think we should assume that's going to happen at all," Sen. Dick Durbin of Illinois said.
"I don't think we should race to a conclusion here," Durbin told CBS' The Early Show. "Ordinarily it takes six to eight weeks to evaluate a Supreme Court nominee. We shouldn't rush to judgment."
However on the divisive issue of abortion, Durbin expressed concern. Asked if he was worried about Alito overturning Roe v. Wade, Durbin said, "Yes, I am. The same element that managed to oust Harriet Miers is jubilant about Sam Alito. What do they know that the rest of America doesn't know?"
CBS News legal analyst Andrew Cohen said the confirmation fight could get ugly.
"If you are looking to the radar screen for signs of dark skies and bluster ahead, the Alito nomination is simply," said Cohen. "A looming Category 5, nasty, spitting, roiling, barking dogfight."
Mr. Bush nominated Alito to the Supreme Court on Monday as a substitute for White House counsel Harriet Miers, who withdrew last week after conservatives refused to support her. Other critics also said she wasn't qualified.
But Alito found steadfast support after Mr. Bush announced his selection, with GOP senators saying he deserved a Senate confirmation vote and threatening to eliminate judicial filibusters if Democrats try to block the White House's newest high court nominee.
"If someone would filibuster ... I would be prepared to vote to change the rules," said Sen. Mike DeWine, R-Ohio.
DeWine is one of the 14 centrist senators that Democrats need to sustain a filibuster of a Supreme Court nominee. Without the group's seven Republicans, Democrats would not be able to prevent Senate Majority Leader Bill Frist, R-Tenn., from abolishing judicial filibusters and confirming judges with just the Senate's 55-member Republican majority.
Under existing Senate rules, it takes up to 60 votes to end a filibuster and force a final vote.
Frist said he's ready to move against judicial filibusters, using what Republicans call the "constitutional option."
"If a filibuster comes back, I'm not going to hesitate," he told Fox News.
Conservatives are much more comfortable with Alito than they were with Miers because of his conservative track record as a federal judge, prosecutor and a Reagan administration lawyer.
Miers had never been a judge.
The nomination got Mr. Bush on the good side again of conservative and anti-abortion groups, who declared Alito a winner after opposing Miers.
James Dobson, founder of Focus on the Family Action, said he was "extremely pleased," and the anti-abortion Operation: Rescue declared that the country was on "the fast-track to derailing Roe v. Wade as the law of the land."
Mr. Bush, who has seen his standing eroded by the insurgency in Iraq, rising fuel prices, Hurricane Katrina mistakes, the indictment of a top aide to Vice President Dick Cheney and Miers' nomination, emphasized Alito's work on "thousands of appeals" and "hundreds of opinions" when he introduced the candidate to the nation Tuesday.
"He has a deep understanding of the proper role of judges in our society," Mr. Bush said at the White House. "He understands that judges are to interpret the laws, not to impose their preferences or priorities on the people."
Alito pledged to uphold the duty of a judge to "interpret the Constitution and the laws faithfully and fairly, to protect the constitutional rights of all Americans, and to do these things with care and with restraint."
Democrats, however, are deeply suspicious of Alito, with Senate Democratic leader Harry Reid of Nevada wondering aloud "why those who want to pack the court with judicial activists are so much more enthusiastic about him" than Miers.
Alito upheld a requirement for spousal notification in an abortion case more than a decade ago, although Senate Judiciary Chairman Arlen Specter — an abortion rights Republican — insisted that doesn't mean Alito would rule to overturn Roe v. Wade, the 1973 ruling that established abortion rights.
Earlier this year, with O'Connor casting the deciding vote, the high court threw out a death sentence that Alito had upheld in the case of a man who argued that his lawyer had been ineffective.
Republicans, meanwhile, returned to their insistence that all judicial nominees deserve hearings and confirmation votes - something they denied Miers.
"I expect the Judiciary Committee to conduct a fair and dignified hearing in a timely manner, followed by an up or down vote by the Senate," said Sen. Charles Grassley, R-Iowa, and a member of the Senate Judiciary Committee.
Mr. Bush's first nominee this year, John Roberts, is now chief justice.
Editor's Note: An earlier version of this story incorrectly stated that "nuclear option" was a Democratic term.