(CNN) - CNN has confirmed that Arizona’s popular Democratic governor, Janet Napolitano, will endorse Barack Obama. The endorsement could prove useful in the upcoming caucuses in Nevada, where Napolitano is expected to join Obama on the trail this evening.
Napolitano is the most prominent Democrat in Arizona, which is one of more than 20 states holding a Democratic presidential primary on "Super Tuesday," Febuary 5. Her backing, especially as a female elected official, is considered a big boost for his campaign in the state.
Napolitano plans to join Obama as he campaigns in neighboring Nevada, the sources said.
Obama received another big boost in South Carolina on Thursday when Sen. John Kerry, the 2004 Democratic presidential candidate four years ago, announced he's endorsing the U.S. senator from Illinois.
UPDATE: In a conference call with reporters, Napolitano praised Obama for his "leadership and
vision" and said she was endorsing him because "we need a new message of hope and solidarity of coming together in Washington."