Ever since Donald Trump chose Indiana Governor Mike Pence as his running mate, there has been speculation that the Republican Party's 2016 ticket would be a difficult marriage between the volatile presidential candidate and his conservative vice-presidential candidate. And tonight's VP debate could widen the alleged rift between them - unless Trump has made peace with some of his formal rivals who once opposed him.

To prep for the big event, Virginia Senator Tim Kaine - Hillary Clinton's VP candidate - has been staging mock debates with Washington lawyer Robert Barnett standing in for Pence. And Pence has been practicing with Wisconsin Governor Scott Walker standing in for Kaine. Pence's choice is a bit odd considering Walker's feelings toward Trump. Let's just say there's enough bad blood between these two to fill the elevator in The Shining.

Just over a year ago, Walker was one of what felt like a hundred rivals for the 2016 Republican nomination. But he abruptly called off his campaign in September 2015. 

"Today, I believe that I am being called to lead by helping to clear the field in this race so a positive, conservative message can rise to the top of the field," Walker said at a press conference in Madison, Wisconsin. "With this in mind, I will suspend my campaign immediately."

And he urged his fellow rivals to follow his example.

"I encourage other Republican presidential candidates to do the same so that voters can focus on the limited number of candidates who can offer a positive, conservative alternative to the current frontrunner."

That frontrunner was none other than Donald Trump. So Walker bowed out in hopes that another candidate could galvanize support and defeat The Donald. Walker personally pinned his hopes on Texas Senator Ted Cruz, whom he endorsed last March. Trump wasn't exactly gracious about being snubbed by the Wisconsin governor.

But in May 2016, Walker and other Republicans who opposed Trump reluctantly endorsed Trump in order to unite the party ahead of Election Day. But Walker's tepid endorsement cooled very fast. A month later, he retracted his support after Trump claimed the judge hearing a case involving Trump University was unfit for the job. Last June, the Republican presidential nominee said Federal District Judge Gonzalo Curiel could not treat the case impartially because of his Mexican heritage.  

“I’m building a wall, it’s an inherent conflict of interest,” Trump said. In other words, Judge Curiel might be racially biased against Trump because of The Donald's arguably racist plan to build a wall around the Mexican-American border. Or in other words, the proverbial pot is calling the kettle black.

Walker wasn't amused. A few days after the story broke, he distanced himself from Trump and the 2016 election in general. 

"It's just sad in America that we have such poor choices [for president] right now," he told ABC-affiliate WKOW. But in the same interview, he said he hoped to change Trump's mind about Mexican-Americans. "I want to make sure he renounces what he says - at least in regards to this judge."

But if you've watched the news lately, you know that Trump hasn't toned down his racial rhetoric. So we have to wonder why Walker is working with the Trump campaign by rehearsing with Pence. Perhaps he's once again onboard with "making America great again," or maybe this is the latest sign of turmoil within the Republican ticket.

Banner image: Wisconsin Governor Scott Walker speaks in Concord, New Hampshire, USA, on March 14, 2015 (Andrew Cline)