Analysis: Rivals still searching for formula to stop Trump

MIAMI (AP) — Nine months after Donald Trump became a presidential candidate, his rivals are still searching for a formula to stop his improbable political rise.

Trump leads his rivals in the all-important delegate count after 24 voting contests, thrusting Republican elites into a tailspin of hand-wringing and denial.

Rubio and Ohio Gov. John Kasich, the last two candidates who have backing within the Republican establishment, face sudden-death primaries in their home states on Tuesday — a pair of winner-take-all contests that could put Trump's lead out of reach.

[...] there were just as many moments where the candidates let Trump slide, including on his acknowledgement that he's exploited immigration laws to bring skilled overseas workers to the U.S. to work for his companies and on his call for sending up to 30,000 U.S. ground troops to the Middle East to fight the Islamic State.

The prospect of Trump winning the nomination has prompted some outside groups to start putting millions of dollars in television advertisements on the air to build a late case against him, including in Florida.

The ads have largely focused on Trump's questionable business dealings, including legal action against the educational company Trump University.