WASHINGTON - It is an unofficial custom for a state's junior senator to be overshadowed by his more senior counterpart, whose longevity is rewarded with a leadership perch and corresponding political muscle.

As the Monroe County native asks voters to keep him in Washington for the the next six years, the immigration debate stands out as a watershed in the past six. A former state and federal prosecutor, he already had been navigating the federal bureaucracy to give state police more power to enforce federal immigration laws. So when Bush went full throttle into comprehensive immigration reform - the kind that includes a pathway to citizenship for some undocumented workers - Sessions felt a vacuum and stepped in.

He mobilized his staff to do opposition research; he became a leading advocate of building a 700-mile fence along the country's southern border; he camped out on the Senate floor for hours at a time to lecture his colleagues; and conservative media pundits seemed to have him on speed dial. Sessions had found his niche.

"That was not something I ever expected to be involved in. One group even reminded me that they had come to me the year before and asked me to be active on immigration, and basically I didn't agree to do so," Sessions said in a recent interview about his campaign for a third term