Delving anew into an explosive issue, President Barack Obama stood near the border with Mexico on Tuesday and declared it more secure than ever, trying to build pressure on Republicans to take on a comprehensive immigration overhaul—and eagerly working to show vital Hispanic voters that he is not the one standing in the way. Countering Republican calls to focus on border security before moving to a comprehensive overhaul, Obama said their demands have been more than met by his administration but "they'll never be satisfied." He boasted of increasing border patrol agents, nearing completion of a border fence, and screening...