Less than one month before the first competitive special House election of 2009, both sides are beginning to ratchet up the rhetoric and call in reinforcements.

While the candidates in New York’s 20th district held their first debate Tuesday, two conservative groups gave notice that they plan to do all they can to boost state Assembly Minority Leader Jim Tedisco, the Republican nominee in the special election.

The U.S. Chamber of Commerce on Tuesday announced that it was endorsing Tedisco, who is battling venture capitalist Scott Murphy (D) in the March 31 contest.

“James Tedisco is a champion for the people of New York and an invaluable leader on important business issues,— Bill Miller, the chamber’s senior vice president and political director, said in a statement. “The Chamber believes he will be an effective legislator and supporter of businesses of every size if elected.—

Meanwhile, a fairly new conservative political action committee, Our Country Deserves Better Committee PAC, announced that it would begin airing TV and radio ads in the district beginning this weekend. According to the group, the ad buy in the Albany and New York City media markets “is expected to reach well into the hundreds of thousands [of dollars] by Election Day.—

The PAC was started in recent months by several well-connected Republican operatives and former elected officials in California. The group has previously aired ads across the country criticizing President Barack Obama and defending Alaska Gov. Sarah Palin (R). The group will preview its New York ads on its Web site Thursday.

But it wasn’t all that easy to tell which candidate was the Republican when Tedisco and Murphy held their first debate, sponsored by the AARP, Tuesday at a library in Saratoga Springs. According to a live feed of the debate provided by WRGB-TV in Albany, both candidates vowed to fight to boost economic development programs in the district and pledged to work to make government more open and accountable.

And because the debate was sponsored by a senior citizens’ group, both candidates spoke at length about the seniors in their lives — Tedisco cited his 93-year-old mother and Murphy referenced his 94-year-old grandmother.

Murphy cast himself as a political newcomer who, through his businesses, has “gotten involved in creating jobs and helping communities.— He also frequently mentioned his desire to move Obama’s agenda and sought to tie himself to Sen. Kirsten Gillibrand (D-N.Y.), who held the 20th district seat for two years before being appointed to the Senate in late January.

Tedisco said he has also created jobs during his 26 years in the Legislature and promised to do more of the same in Congress.

“I’ll lead the fight to hold the people who created this fiscal crisis accountable,— he said.

But Tedisco refused to say whether he would have voted in favor of the economic stimulus package that passed Congress last month — a point that Democrats and local editorial boards have been hammering for the past two weeks. During the debate, the Republican did say he would have tried to eliminate much of the pork from the bill.

With 70,000 more enrolled Republicans than Democrats, the 20th district seat represents a major pickup opportunity for Republicans, and national GOP leaders have made the race a top priority.

But Murphy is not without his outside support. He has been boosted in recent days by news that he has been endorsed by the New York AFL-CIO and that he will appear on the ballot as the nominee of the centrist Independence Party. Murphy is due to be in Washington, D.C., for a fundraiser with Congressional leaders this evening.