MIAMI — Two years removed from an immigration swoon, Sen. Marco Rubio is poised to enter the presidential sweepstakes a major contender reinvigorated by dogged focus and expertise on international affairs.

The Florida Republican’s 2013 drive to sell comprehensive immigration reform fell flat with many conservatives. Bipartisan “gang of eight” legislation Rubio negotiated cleared the Senate. But the GOP-controlled House rejected the bill, and grassroots activists who championed Rubio during his Tea Party-fueled 2010 Senate victory reconsidered their affection. At issue: the bill’s provision creating a conditional path to legalization and possible citizenship for illegal immigrants.