Kasich calls Cruz a 'smear artist'

Crossfire finally has erupted on one of the few peaceful fronts of the Republican presidential primary, between Texas Sen, Ted Cruz and Ohio Gov. John Kasich.

Until now, the candidates hardly had mentioned each other on the campaign trail, and largely refrained from exchanging harshly-worded rebukes. By Monday, they'd apparently left the friendly stage behind them.

It signals Kasich's shift from a largely inconsequential candidate to one whose tiny cache of delegates could actually sway the nominating process.

Both of the leading GOP candidates, Cruz and frontrunner Donald Trump, think they would benefit from Kasich getting out of the way. Both have called from him to leave the race.

RELATED: Trump calls on Kasich to quit race: 'He's taking my votes'

Cruz took it a few steps further this weekend, launching its first overt attack on Kasich with a round of mailers and a video spot in Wisconsin, according to media reports.

The attacks homed in on an alleged tax credit scandal during Kasich's term as Ohio governor.

Kasich responded in kind, offering his strongest-yet reproach of Cruz.

"They've spent, I don't know, a million dollars smearing me — Ted, Senator Ted, the smear artist," Kasich said, according to the Washington Post. "For a guy that's not doing very well, they sure are spending a lot of money trying to knock me out."

Wisconsin's Tuesday primary could strongly affect the direction of the Republican race. An overwhelming win by Donald Trump likely would dispel any hope of another candidate winning an outright majority of delegates before the party's July convention.

A win by Cruz, who is favored in most state polls, would keep him in the running, and push the party another big step toward a contested convention.