Trump alleges rival Cruz is bribing delegates

Republican presidential front-runner Donald Trump is accusing rival Ted Cruz of bribing delegates to the national convention to build support for Cruz's candidacy.

Trump offered no evidence to back up his accusation while campaigning in Maryland, one of a handful of states that will be voting Tuesday.

Speaking in an airplane hangar in Hagerstown on Sunday evening, Trump repeatedly stressed that he expects to win the number of delegates needed to land the nomination on the first ballot at July's national convention.

"I think we get that 1,237," he says. "I'm pretty sure."

Cruz has badly outmaneuvered Trump by ensuring that supportive delegates make it to the convention. Trump has repeatedly slammed the system as "rigged."

Cruz and rival John Kasich are hoping to force a contested convention in which delegates would be free to support them after the first ballot.

In the meantime, Democratic presidential candidate Bernie Sanders is urging Hillary Clinton to join him in support of a tax on carbon emissions to curb climate change and support universal health care.

Sanders is addressing more than 7,000 people at a Providence, Rhode Island, park ahead of the state's primary on Tuesday.

Sanders says if the former secretary of state is "concerned about climate change" she should join him in pushing for a tax on carbon.

He also says Clinton and the establishment don't think the nation has "the guts" to take on the insurance and drug industries to provide universal health care.

Rhode Island allows independents to participate in the Democratic contest and Sanders' campaign hopes the senator's message will power him past Clinton in the primary.