Yvonne Wingett Sanchez, and Dan Nowicki

The Republic | azcentral.com

Donald Trump, whose grip on Arizona's 11 electoral votes appears to be in jeopardy, will appear in downtown Phoenix for a Saturday rally, his seventh Arizona event this election season.

His appearance at the Phoenix Convention Center marks the most appearances by a Republican presidential nominee in decades, according to Arizona Republic research.

Doors open at 12:30 p.m. and Trump will take the stage around 3:30 p.m. (Get your tickets here.) Warm-up guests likely will include state Republican Party Chairman Robert Graham, Trump's national campaign Chief Operating Officer Jeff DeWit and Maricopa County Sheriff Joe Arpaio.

Trump's son, Donald Trump Jr., stumped for his father at Arizona State University on Thursday and confirmed his father would return to Phoenix on Saturday.

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Trump's campaign stop comes as his Democratic rival, former U.S. Secretary of State Hillary Clinton, has increased its advertising efforts by $2 million and dispatched big-name surrogates to try to boost voter turnout in an effort to change the traditional red state blue.

The Democratic focus on Arizona has put the Trump campaign on alert in a state that has been carried by a Democratic presidential candidate just once since President Harry Truman won the state in 1948. President Bill Clinton, in his 1996 re-election race, defeated Republican Bob Dole here.

Trump is struggling in Arizona despitehis six rallies and another two solo visits by Indiana Gov. Mike Pence, his vice-presidential running mate.

An Oct. 10-15 Arizona Republic/Morrison/Cronkite News poll showed Clinton leading Trump by five percentage points in a race that political observers say could go either way based on turnout. Clinton was supported by 39 percent of the likely Arizona voters surveyed, while Trump was backed by 33.9 percent. Another 20.7 percent still hadn't decided yet who to vote for in the Nov. 8 general election. The statewide telephone poll was conducted after the combative second presidential debate and after release of an 11-year-old video in which Trump made vulgar remarks about women.

The Phoenix Convention Center has been the backdrop of two key moments in Trump's White House bid.

His then-nascent presidential campaign held a raucous rally at the Phoenix Convention Center in July 2015, where he needled his GOP primary rivals and "incompetent politicians," including the state's senior U.S. Sen. John McCain. He returned to that venue in August for a much-anticipated address on immigration, where he doubled down on his hard-line stance despite speculation he might soften his policy prescriptions to broaden his appeal to general election voters.

Here's what's in Donald Trump's 10-point immigration plan

Follow the reporter on Twitter and Facebook. Reach her at yvonne.wingett@arizonarepublic.com or 602-444-4712.