Barack Obama is taking a rearguard action while Hillary makes her play for the Hispanic vote. The Hill reports:

This week's charged Senate debate over immigration may give Sen. Barack Obama (D-Ill.) a chance to chip away at Sen. Hillary Rodham Clinton's lead with the crucial Hispanic voting bloc.

The New York Democrat won the prized endorsement last week of Los Angeles's Hispanic mayor, Antonio Villaraigosa, but Obama is working closely with Sen. Robert Menendez (D-N.J.), one of a handful of nationally known Latino officials yet to endorse a presidential candidate. [emphasis added]

Taking a break from the presidential campaign trail, Obama this week will be visible on Capitol Hill, as the Senate resumes work on its immigration bill. He is cosponsoring four amendments, including two with Menendez, to the legislation, which would create a path for citizenship for the 12 million immigrants in the country illegally. And this Saturday, Obama's campaign plans to highlight his work as volunteers go door to door in a host of cities, including several with major Hispanic populations, to support his candidacy.

Sen. Barack Obama is unlikely to vote for an immigration reform measure this week unless changes are made to address his concerns about temporary workers.

"I'm not going to vote for something if I think ultimately that it's going to repeat mistakes of the past and not going to solve the problem," Obama told reporters Monday. "At the end of the day, if I don't think it's quite there, it'll have to wait until I'm president."

Obama's comments came after he and two fellow Democratic presidential candidates addressed more than 500 people gathered for the Rev. Jesse Jackson's annual Rainbow PUSH Coalition conference at the Hyatt Regency O'Hare in Rosemont.

The senator said he is concerned the temporary worker provision in the immigration measure under consideration would create "second-class workers" who would be forced to go home every two years without acquiring any rights.