Senate's failure to advance transformative border legislation prompts GOP shift.
Previously declared "dead on arrival," bipartisan immigration reform sees new light.
GOP's slim majority prompts strategic retreat from border demands.
Senate negotiators grapple with bipartisan consensus amid polarized landscape.
McConnell stresses high stakes, urges optimism in Ukraine aid talks.
White House maintains pressure on Congress to fund national security priorities.
House Speaker Johnson emphasizes security concerns at U.S.-Mexico border amid funding negotiations.