Mitt Romney's venture into campaigning comes 10 days after he offered a withering take down of Donald Trump. (Reuters)
Mitt Romney, the 2012 Republican nominee who has slammed current frontrunner Donald Trump, campaigns with Governor John Kasich today, ahead of Ohio's crucial primary, sources in both camps said.
The appearances will be the first for Romney on the 2016 campaign trail, although he is not endorsing Kasich, a source close to Romney said.
The party's 2012 standard-bearer has indicated he will seek to help the three remaining non-Trump candidates -- Kasich, Senator Ted Cruz and Senator Marco Rubio -- any way he can, as the party's establishment grapples for ways to derail Trump.
He will appear today with Kasich in North Canton and at Kasich's hometown rally near Columbus in the evening, Kasich's team confirmed late on Sunday.
Romney's venture into campaigning comes 10 days after he offered a withering take down of Trump, saying in a speech in Utah that the billionaire real estate mogul was "a phony, a fraud," and that he has "neither the temperament nor the judgment to be president."
Trump has responded in kind, blasting Romney as a washed-up establishment figure who was too weak a candidate to defeat President Barack Obama.
Kasich is a popular two-term governor and he leads Trump narrowly in polling in Ohio. But Trump has a commanding lead in the all-important national race to secure the majority of delegates who go to the party convention, where they elect the Republican nominee.
Trump's shock success in the primaries has alarmed the Republican establishment.
Romney warned early this month of "profound consequences for the Republican Party," and that "if we Republicans choose Donald Trump as our nominee, the prospects for a safe and prosperous future are greatly diminished."
Trump has been campaigning hard in Ohio in recent days, and hosts a rally in Youngstown today evening after an appearance in Florida, a large and critical state which also votes on Tuesday.
On Sunday he blasted Kasich for voting while he was a congressman for the North American Free Trade Agreement, which has been blamed for hundreds of thousands of lost Ohio jobs since it was implemented in the 1990s.