Republicans from the five counties that make up the 19th Congressional District have picked political newcomer Kieran Lalor, 32, of Peekskill to challenge Democratic incumbent John Hall in November.

Lalor, a Marine Corps reservist and Pace University Law School graduate, defeated Westchester legislature Republican Minority Leader George Oros of Cortlandt and former GOP congressman Joseph DioGuardi of Ossining.

Republican committee members from Putnam, Westchester, Rockland, Dutchess and Orange counties gathered Thursday night at Villa Barone Hilltop Manor catering hall in Mahopac to choose a unity candidate in one round of voting. The National Republican Congressional Committee has targeted Hall, a freshman from Dover Plains, as one of the top Democrats in the Northeast to defeat.

Oros said yesterday he is preparing for a Republican primary in September.

"I went into this knowing there would be a primary," said Oros, who expected a primary challenge from Lalor had he won. "I'm prepared to take my message to the voters in the 19th in a primary and the general election."

DioGuardi, who had not formally announced his candidacy and finished a distant third in the vote, said he would support the candidate backed by the party.

It was the first time in more than a decade that Republican committees from the five counties had come together to select a candidate to run for the congressional seat, said Michael Bartolotti, vice chairman of the Putnam County Republican Party.

Hall defeated Sue Kelly, R-Katonah, a six-term incumbent, with 51 percent of the vote in November 2006.

Dutchess County Chairwoman Corinne Weber said Lalor got 347 of the committee votes to 311 for Oros and 107 for DioGuardi.

Westchester GOP Chairman Douglas Colety described Lalor as "an energetic candidate with fire in the belly who had worked the grassroots and the district leaders in the months leading up to the convention."

Colety said Republicans are united behind Lalor as the endorsed candidate but would back the candidate who wins the Sept. 9 primary.

Lalor said yesterday his biggest adjustment is getting used to becoming a funded Republican Party candidate overnight.

"I've been an outsider running a campaign on a shoestring," said Lalor, who worked as a security guard while going to law school full time. "I won over a major Republican insider."

The primary challenge promised by Oros would be "a nuisance" that would drain resources needed in the race against Hall, Lalor said.

Hall had $1.1 million in unspent funds as of March 31, according to a report filed with the Federal Election Commission. He has been one of the top fundraisers among House freshmen.

Lalor trailed in fundraising with $86,873 at the end of March.

Oros, who entered the race in February and got the backing of Kelly and former Gov. George Pataki, had $52,406 at the end of the first quarter.

Dennis Sant, newly elected chairman of the Southeast Republican Committee, said he was "surprised and pleased" by Lalor's selection. Though he recognizes the role of primaries in the democratic process, Sant said they "take a great toll on funds" that should be spent to defeat the other party.

Lalor, who supports a continued U.S. presence in Iraq and Afghanistan, said he would spend the Memorial Day weekend working on how best to bring his platform before voters. At the top of his agenda is energy independence, which he said would be achieved by "drilling more, refining more and taxing and regulating less." At the same time, the private sector would be expected to come up with alternatives to gas, Lalor said.

His plan to stimulate the economy includes making the tax cuts put in place by the Bush administration permanent while cutting spending.

Lalor, who has a young daughter with a heart condition, said he opposes a single-payer plan of health-care reform. Instead, he favors savings accounts from which people could take money to spend on health care as they choose.

Darren Rigger, Peekskill's Democratic Party chairman and Hall's newly appointed fundraiser in the district, said Hall is taking the Republican challenge very seriously.

"He knows how tough a race this is going to be," said Rigger, who ran in the primary against Hall in 2006. "He's not taking anything for granted. Hall won by the skin of his teeth, and he's working for every vote."