Florida Governor Ron DeSantis ends presidential campaign, endorses Donald Trump before New Hampshire primary. DeSantis' departure leaves Nikki Haley as Trump's last remaining challenger. Majority of DeSantis supporters likely to switch allegiance to Trump. Trump holds lead over Haley in New Hampshire and South Carolina. DeSantis' exit unlikely to change campaign dynamics. Haley sharpens attacks on Trump. DeSantis' decline due to flawed campaign strategy and Trump's popularity. DeSantis' late entry, glitch-filled campaign launch, and mismanagement of funds contributed to downfall.