CNN

(CNN) – Dick Cheney's decision to weigh in on the Republican intra-party battle in Texas - a rare primary season endorsement by the former vice president - is an attempt to help challenger Kay Bailey Hutchison shore up her conservative credentials and attract undecided GOP voters, according to two knowledgeable GOP sources.

The former vice president teamed up with Hutchinson in Houston Tuesday to officially endorse her gubernatorial bid. The Texas senator is taking on two-term incumbent Gov. Rick Perry in next year's Republican primary.

One source notes that Cheney and Hutchison have a longstanding relationship that goes back to the days when they were both in Dallas, a time when Cheney served as Halliburton CEO.

The political calculation behind Tuesday's move is the hope that Cheney can help the senator win over undecided Republican voters in a state where the Bush administration's seal of approval may hold more sway than anywhere else. "The two most popular people in Texas are George and Barbara Bush - and Cheney isn't far behind," says one source close to Texas politics.

Perry, according to his campaign, has already won a re-election nod from the person who had hoped to succeed Cheney - Sarah Palin.

But Palin's popularity won't necessarily translate into major support for Perry. Some rank-and-file Republicans are concerned about Perry's ethical imbroglios. The fact that his party lost seats in the statehouse in the last election has also contributed to GOP dissatisfaction with Perry.

Still, one controversy might actually pay dividends for Perry: His headline-grabbing remarks suggesting Texas, unhappy with the administration's economic policy, could want to secede from the union. "That helps him," according to the Texas source. "There's no love for Washington."

Despite his time in Washington, he adds, Cheney isn't viewed as a Washington insider - he's seen as a man who tangled with the city's establishment.