After spending several hundred thousand dollars laying what appeared to be the groundwork for a U.S. Senate run, Merrimack investor Fred Tausch abruptly changed course yesterday, announcing that he would not seek office in 2010.

Tausch, who turns 38 this month and who recently moved from Nashua to Merrimack, had become a presence at Republican meetings and on the state's airwaves, starring on frequent politically oriented television ads and radio commercials, in which he decries what he sees as government waste. Tausch paid for the ads himself.

The announcement comes only days after former attorney general Kelly Ayotte filed papers to explore a bid as a Republican for Senate. Ayotte appears to be the favorite of many leaders in the state's GOP. She's been talked up by departing Republican Sen. Judd Gregg and, reportedly, supported by former governors Steve Merrill and Craig Benson.

Tausch's decision also comes days after the Monitor ran a profile of Tausch that explored his unorthodox political past - he appears to have defended long-shot Democratic candidate Mike Gravel in online postings in 2007 and donated to President Obama in 2008 before billing himself as a Republican this year - and Tausch's ties to New Hampshire, where he appears to have moved within the past two years. Tausch has roots in Massachusetts and previously lived and worked in New York City for a hedge fund and for a business of the dot-com era.

In a statement yesterday, Tausch said he had been encouraged to run and pledged to keep up his efforts to fight government waste.

"Many Republicans have encouraged me to be their voice as a candidate for office next year. It was an honor to be approached, and I gave the prospect serious consideration. But after careful deliberation, I've decided not to enter public service at this time," Tausch said in the statement.

Tausch burst onto the scene this winter, calling himself a disappointed former Obama supporter who opposed the $787 billion federal stimulus package. He called his campaign STEWARD, for Stimulate the Economy Without Accumulating Record Debt, and he originally pledged to spend $100,000 of his own money opposing the stimulus.

That amount - along with speculation about Tausch's political intentions - ballooned as months passed. Tausch spent nearly $400,000 on television and radio ads that featured him decrying federal bailouts, plus more on several mailers, ad production, an economic study of the bailout's impact, at least three political staffers, a professional website and a poll.

Tausch had hired political strategist Mike Dennehy of Concord, a veteran of John McCain's presidential campaigns. Many of Tausch's mailers directly targeted Rep. Paul Hodes of Concord, the only Democrat in the Senate race.

It remains unclear what, exactly, will become of STEWARD or what Tausch's long-term plans are. In yesterday's statement, Tausch vowed to continue speaking out for those who want to "hold politicians' feet to the fire" and vowed to have STEWARD keep up its fight. Asked directly whether STEWARD would continue its ad or mailer campaign, spokesman Jeff Grappone declined to answer. According to the Union Leader, Tausch did not renew his ad campaign on WMUR.

For the amount of money he spent so early in the election cycle, Tausch's noncampaign is highly unusual in New Hampshire, said University of New Hampshire political science professor Dante Scala. To get wide name recognition, Scala said, Tausch would have had to significantly revive his spending - and in an election cycle where party leaders found a clear favorite in Ayotte.

"That's a lot of chips to put in the middle of the pot," he said.