With New York on their minds, Democrats trade fresh attacks

While Clinton escalated her attacks against rival Bernie Sanders, Republican leader Donald Trump complained about a "rigged" nomination process prompting a fierce defense from party leaders.

At a rally in Rochester on Sunday, Trump had blasted the way the country chooses presidential party nominees as "corrupt" and "crooked" — a sentiment echoed by surrogates and supporters who appear increasingly troubled by Cruz's superior efforts when it comes to wrangling delegates.

In an interview with conservative radio host Mike Gallagher, Reince Priebus, chairman of the Republican National Committee, pushed back against Trump's claims, saying that the convention system used in Colorado is not an affront to the people of Colorado.

Sanders hit back at a rally in the upstate New York city of Binghamton, rallying supporters with a lengthy rift slamming Clinton for promoting fracking as secretary of state and only offering conditional opposition to the practice.

The harsher tone comes just days before the two Democrats will meet on stage for the first Democratic primary debate in more than a month.

Since their last faceoff, the contest has taken a decidedly negative turn, with the two candidates trading a series of barbs over their qualifications for the White House.