ALBANY — Mayor Giuliani’s once commanding lead in the race for New York’s Republican delegates has evaporated and he now trails Senator McCain in his home state, according to two polls released today.

Siena College’s poll also showed Senator Clinton with a 2-to-1 advantage over Senator Obama in her delegate-rich state. But Mrs. Clinton is getting the support of less than half the Democrats polled — 48% to Mr. Obama’s 36% — and Mr. Obama is running strong in New York City, though he still trails Mrs. Clinton there.

Mr. McCain now leads Mr. Giuliani by 12 percentage points, a sharp reversal from the former New York City mayor’s 33-point lead over the Arizona senator in Siena’s December poll. Mr. McCain had the support of 36% of New York Republicans, while Mr. Giuliani had 24% and a former Massachusetts governor, Mitt Romney, had 10%, the latest poll showed.

Mr. Giuliani’s decline in the state he led through the September 11, 2001, terror attacks six years ago surprised many.

“I still think that, despite the fact that Mayor Giuliani has been falling nationally, to see the level of how far he fell in just a month in his home state is stunning,” a Siena poll spokesman, Steven Greenberg, said.

“Trailing in New York is no good for Giuliani, but McCain hasn’t closed the sale,” the director of the Marist College/WNBC poll, Lee Miringoff, said. “This is very much a primary in flux … but the longer (Giuliani) fails to appeal to voters, the worse it gets. And this points out that even here in New York, his problems are notable.”

New York’s primary is February 5, part of the Super Tuesday balloting in 24 states.

The WNBC/Marist poll showed 34% of Republicans, including those “leaning toward” a candidate, favored Mr. McCain, while 23% favored Mr. Giuliani, 15% a former Massachusetts governor, Mitt Romney, and 11% a former Arkansas governor, Michael Huckabee.

Mr. McCain runs strongest upstate, the source of most Republican primary votes. A regular guest on the “The Daily Show with Jon Stewart” — which is influential with its young audience — Mr. McCain beats Mr. Giuliani among college-educated Republicans, 18- to 44-year-olds, moderates, conservatives, and among first time voters in a GOP primary.

For the Democrats, the WNBC/Marist Poll found Mrs. Clinton was favored by 48% of likely Democratic voters, including those leaning toward a candidate. Mr. Obama had 32% and a former North Carolina senator, John Edwards, 9%.

“She’s ahead, it’s a good lead, but she is below 50% and runs pretty close to Obama in New York City, where the lion’s share of the votes come from,” Mr. Miringoff, whose polling is done in conjunction with WNBC in New York City, said. But he noted that 79% of those supporting Mrs. Clinton say they are “strongly committed” to her, while only 58% of Mr. Obama’s supporters say the same.

“Clinton has a good lead, but not huge numbers that she’s going to drive everyone else out of the state,” Mr. Miringoff said.

The Giuliani campaign has shifted its emphasis in recent days from his September 11, 2001, leadership to current economic issues.

Rep. Peter King said Mr. Giuliani will still take New York.

“The people of New York know better than anyone that Rudy is the bold and gutsy leader our country needs right now to tackle the tough challenges,” the Long Island Republican said. “Mayor Giuliani will win New York because voters around the country want a president who has been tested in crisis, is a proven tax cutter and will get results because he’s gotten them before.”

Siena’s Mr. Greenberg said Republican women gave Mr. Giuliani a small edge while Republican men backed Mr. McCain, the Vietnam war hero, by a 3-to-1 margin.

For the first time in a Siena poll, Mr. Giuliani had a higher unfavorable rate — 48% — than favorable. Mr. McCain was viewed favorably by 56% of New Yorkers.

Mr. Giuliani, for years considered a leading Republican candidate for president, has taken a beating from Iowa through New Hampshire to Nevada and South Carolina. He has focused on Florida, believing that if he can score his first win there he will be launched toward a series of victories on Super Tuesday.

Recent polls showed Messrs. McCain, Giuliani, Romney, and Huckabee were close in Florida.

As for the Democrats, Mrs. Clinton still leads Mr. Obama among black Democrats.

“While (Obama) has picked up considerable support with African- and Caribbean-American Democrats, Obama still trails Clinton 46-36% among black Democrats, and Clinton has a 50-18% lead with white Democrats,” Mr. Greenberg said.

Mrs. Clinton had the support of 48% of New York Democrats polled. Mr. Obama had 23%.

“We are gratified by the outpouring of support for Senator Clinton throughout New York, but are taking nothing for granted and working hard for every vote,” a Clinton spokesman, Blake Zeff, said.

New York has 232 Democratic delegates and 101 Republican delegates.

For its New York poll, Siena called 625 registered voters between January 14 and 17. The poll has a margin of error of plus or minus 3.9 percentage points.

The Marist/WNBC poll questioned 1,467 registered voters between January 15 and 17. Its poll has a margin of error of plus or minus 3 percentage points.

There was no immediate comment about the poll results from the McCain or Obama campaigns.