By Eric Bradner, CNN

(CNN) -- The political world is watching Arizona this week as President Donald Trump tries to move past one controversy by wading into another -- visiting his core supporters in the state whose two senators are among his most vocal critics within the Republican Party.

Weeks ago, Sen. John McCain's vote sank Trump's health care bill in the Senate. Sen. Jeff Flake, meanwhile, has voted with Trump -- but he also wrote a book in which he compared Trump's campaign to a "late-night infomercial" with an agenda that is "free of significant thought."

Now, Trump is set to arrive in their backyard Tuesday for a nighttime rally in Phoenix.

It comes a week after the firestorm of criticism from the left and right that he set off last week by equating white supremacists rallying in Charlottesville, Virginia, with anti-racist counterprotesters.

"I am disappointed that President Trump has chosen to hold a campaign rally as our nation is still healing from the tragic events in Charlottesville," Phoenix Mayor Greg Stanton said in a statement last week.

Some of Trump's intra-party critics are urging him to use the Phoenix rally to heal a nation that the President's own words ripped apart.

"When you go, try to use that as an opportunity to say something that's going to bring people together," Ohio Gov. John Kasich said in a comment directed at Trump Sunday on CNN's "State of the Union." Kasich was among the many hopefuls who ran against Trump for the Republican presidential nomination in a heated and lengthy primary.

The visit also gives Trump an opportunity to re-stake his claim on the Republican Party -- potentially by taking on one or both of Arizona's GOP senators.

Among the swirling questions headed into the week: Will Trump endorse a Flake primary opponent?

Last week, Trump tweeted praise for Kelli Ward, the conservative who failed to unseat McCain in a 2016 primary but is trying again by taking on Flake in 2018.

"Great to see that Dr. Kelli Ward is running against Flake Jeff Flake, who is WEAK on borders, crime and a non-factor in Senate. He's toxic!" Trump tweeted.

The tweet roiled Republicans on several levels. First, it threatened to further strain Trump's relationship with Senate Majority Leader Mitch McConnell, the Kentucky Republican whose policy -- through the Senate GOP's campaign arm and a super PAC -- is to back all Republican incumbents against primary challengers.

Second, it came as two Republicans broadly regarded as standing better chances of defeating Flake continue conversations with the White House about entering the race. State treasurer Jeff DeWit and former state party chairman Robert Graham have been expected to decide about a run in the coming months.

Adding to the tension, Trump appeared to hint recently that he may pardon former Maricopa County Sheriff Joe Arpaio -- a lightning rod for more than a decade in the immigration battle, and who was found guilty last month of refusing to follow a judge's order barring him from racial profiling Latinos. Phoenix is in Maricopa County. Trump retweeted a story from Fox News last week that reported he was "seriously considering" pardoning Arpaio.

In his statement, Stanton said: "If President Trump is coming to Phoenix to announce a pardon for former Sheriff Joe Arpaio, then it will be clear that his true intent is to inflame emotions and further divide our nation."

Trump's trip -- and the focus on the region's Republican senators -- highlights the Southwest's emergence as the center of the political world not just this week, but moving forward.

The frenetic week in Arizona politics kicks off early Monday morning when Flake attends a breakfast hosted by the Gilbert Chamber of Commerce in the Phoenix suburbs.

Flake in Arizona and Sen. Dean Heller in Nevada -- who waffled for weeks before ultimately siding with Trump on the failed health care vote in the Senate -- are the two Republicans in most jeopardy of losing their seats in the 2018 midterms.

Both already face primary challengers, Flake against Ward and potentially more candidates and Heller against Danny Tarkanian, the son of the legendary University of Nevada at Las Vegas basketball coach Jerry Tarkanian. And both appear set to face top-tier Democratic challengers if they advance to the general election.

Meanwhile, just to the west in California, a swath of seven House seats, mostly located in or near Orange County, is a crucial battleground in Democrats' effort to retake control of the chamber in the midterms. All seven are held by Republicans but were areas carried by Democratic presidential nominee Hillary Clinton in 2016.

Arizona, meanwhile, was a Trump state in 2016 -- but it was closer than traditional swing states Ohio and Iowa. That fact underscores why Democrats' long-term hopes are increasingly moving from the Rust Belt to competitive Sun Belt states like Georgia, Arizona and Texas, where changing demographics could eventually shift the traditionally safe GOP terrain.