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 yesterday.

Siena College’s poll also showed Democratic Senator Clinton with a 2-to-1 advantage over Illinois Senator Obama in her delegate-rich state. But Mrs. Clinton is getting the support of less than half the Democrats polled — 48% to 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 Giuliani had 24%, and former Massachusetts Governor Romney had 10%, the latest poll showed.

Mr. Giuliani’s decline in the state he led through the September 11 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 Mr. Giuliani, but Mr. McCain hasn’t closed the sale,” Lee Miringoff of the Marist College/WNBC poll said. “This is very much a primary in flux … but the longer (Mr. 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% Mr. Romney, and 11% Governor 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 Republican 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 Senator Edwards 9%.

“She’s ahead, it’s a good lead, but she is below 50% and runs pretty close to Mr. 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.

“Mrs. 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 Sepember 11 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 county needs,” he said.