Amy Walter reports: GOP Rep. Jason Chaffetz of Utah, a rising star in the Tea Party movement and a fixture on cable news circuit, surprised many in Washington and his home state by announcing that he would not challenge Sen. Orrin Hatch in a GOP primary. At a hastily convened press conference this afternoon in Salt Lake City, Chaffetz said he would seek re-election to the House so that he could continue his efforts to tackle the federal budget. In a statement, Chaffetz wrote: “Ultimately, I can spend the next 15 months doing my job, or I can spend the next 15 months campaigning to do Senator Hatch’s.” Chaffetz was widely expected to challenge the six-term Senator. He’s popular with the conservative activists in the state. He’s experienced at beating incumbents: He won his Provo-based seat in 2006 by knocking off Rep. Chris Cannon with 60 percent of the vote. And, he’s been mulling this run for months, even taking a statewide town hall tour this month. Most important, the nominating system in Utah gives oversized influence to conservative activists. In order to even get on a primary ballot, you have to win at least 41 percent of the approximately 3,500 delegates at a Republican convention. In 2010, Republican Sen. Bob Bennett lost his bid for a fourth term when he took just 27 percent of the vote in a three-way race at the convention. Credit, however, has to go to Hatch, who took the Tea Party threat seriously. After watching many of his colleagues lose primary challenges in 2010, Hatch began a concerted effort to woo Tea Party types. He tacked hard to the right on policy (most recently with his vote against raising the debt ceiling). And, his campaign organization, said one GOP insider, has put together an amazing ground game. He even promoted an endorsement from conservative media personalities like Mark Levin and Sean Hannity. Even so, Hatch isn’t completely out of the woods. While Chaffetz has to be considered his biggest threat, it doesn’t mean that other Republicans are going to pass at the opportunity to challenge Hatch at the convention. FreedomWorks for America, which has been hosting a “Retire Hatch” campaign, remains committed to keeping up the fight. In a statement immediately following Chaffetz press conference, National Political Director Russ Walker said: “We are confident a principled fiscal conservative will enter the race to defeat 36-year big government incumbent Sen. Orrin Hatch.” “Sen. Hatch voted for TARP, the Fannie Mae and Freddie Mac bailout, against a ban on earmarks and was the lead sponsor of an individual mandate in health care,” FreedomWorks Utah field coordinator Dan McCay said. “Utahns believe it’s time for Sen. Hatch to step down and while Rep. Chaffetz will not be the one to replace him, we remain committed to finding someone new.” And, it’s likely that the Club for Growth –- which led the effort to oust Bennett in 2010 -– would also get behind a serious challenger to Hatch. Hatch, however, has proven to be well-prepared for a fight and is sitting on more than $3.4M in the bank.