Hillary Clinton took a monumental step toward clinching the Democratic Party’s White House nomination Tuesday, while Donald Trump`s seemingly unstoppable rush to victory hit a bump in Ohio.Trump won key Republican primaries in Illinois, North Carolina and Florida - where he thumped home state Senator Marco Rubio, who immediately announced he was suspending his presidential campaign."This was an amazing evening," a buoyant Trump told supporters. "We`re going to win, win, win and we`re not stopping."Rubio`s loss was a major setback for Republicans trying to stop the bellicose businessman, whose populist anti-immigrant, anti-Muslim stance they fear will split the party.The 69-year-old Trump was clinging to a narrow lead in Missouri with nearly all of the votes counted, but was denied a clean sweep by Ohio Governor John Kasich, who carried his home state, a key general election battleground.Trump may now struggle to reach the 1,237 delegates necessary to avoid a challenge at the party`s nominating convention in July in Cleveland."The bottom line after tonight: it looks like Trump will not have a majority of delegates in July," said Paul Beck, a professor of political science at Ohio State University.- Big night for Clinton -There were fewer problems for Clinton, who defeated her rival Bernie Sanders in Florida, North Carolina, Ohio and Illinois. She also had a slight edge in Missouri, according to vote tallies.Sanders now face an almost impossible task to catch up with Clinton`s formidable delegate advantage."We are moving closer to securing the Democratic Party nomination and winning this election in November," said Clinton, casting one eye on the general election -- and at Trump."When we hear a candidate for president call for rounding up 12 million immigrants, banning all Muslims from entering the United States -- when he embraces torture, that doesn`t make him strong. It makes him wrong."Republicans will now have to decide whether to rally behind one candidate or siphon votes away from Trump as a team.The scope of Trump`s victory against Rubio in Florida will shock the Republican establishment as much as it will raise hopes the party can challenge in the one-time swing state come November 8. President Barack Obama carried the state in both the 2008 and 2012 elections.