This article originally appeared in Governing Magazine’s Ballot Box blog.

Janet Napolitano is the popular governor of Arizona. Why would she consider giving up such a sweet gig to head the U.S. Department of Homeland Security -- a politically perilous job that would put her in charge of a sprawling bureaucracy -- in President Obama’s administration?

Actually, there are at least five reasons why this is the perfect time for Napolitano to get out of Arizona.

1) The state budget is in crisis. Lots of states of budget shortfalls right now, but Arizona’s situation is far worst than most. The housing bust hit Arizona earlier and harder than most other states. The state patched up a $2 billion shortfall earlier this year.

That wasn’t enough. For the current fiscal year, Arizona now has a $1.2 billion shortfall on a $9.9 billion budget. Cutting out 12% of the budget part of the way through the year is serious business. And, the situation is only supposed to get worse next year. Napolitano has been a very successful governor -- she carried every county in the state in her 2006 reelection bid -- but even her popularity would be tested by the painful budget cuts or tax increases necessary to balance the budget.

2) More Republicans in the legislature. Despite the speculation that John McCain would lose his home state, he ended up winning comfortably and having modest coattails. According to the National Conference of State Legislatures, Republicans gained one seat in the State Senate to take a 18-12 advantage and two seats in the House of Representatives for a 35-25 edge. Democrats thought they had a chance to win one or both houses, but instead, as has been the case for Napolitano’s entire governorship, Republicans will control the legislature.

3) Fewer moderate Republicans in the legislature. Napolitano has been successful throughout her tenure at reaching deals with moderate Republican legislators. Conservatives, though, steadily have been knocking off the moderates in Republican primaries. They defeated more moderates this year. Napolitano would have a tough time striking bargains with the current group of lawmakers.

4) She’s a lameduck. Napolitano is term-limited in 2010. Why stick around for a job she’ll lose in two years anyway?

5) No open U.S. Senate seat. Being a lame duck wouldn’t be much of a problem, if there were an obvious office for Napolitano to pursue in the future. Many people had assumed Napolitano was eyeing John McCain ’s U.S. Senate seat, especially if McCain decided to hang it up in 2010.

McCain, however, is already sending signals that he’ll run for reelection in two years. Some polling has shown Napolitano running strong against McCain, but obviously it would be a tough race, especially given the problems that Arizona state government will face over the next two years. If Napolitano doesn’t want to be in the Senate (really, who would?) or doesn’t think she would beat McCain, the best way to remain a major political figure would be in the Obama administration.

By the way, I’m a tad suspicious of the speed at which McCain declared his intentions to seek reelection. Could it be that he’s trying to encourage Napolitano to go to Washington, rather than run for Senate? His praise for Napolitano after her name leaked as the leading Homeland Security contender was also suspiciously effusive.