Indiana Gov. Mike Pence kicked off his first campaign appearance as Donald Trump's running mate by attacking Hillary Clinton and outlining the contrast between the GOP ticket and the Democrats.

"The choice could not be more clear. The stakes could not be higher," Pence said at a Saturday morning rally.

Pence said Clinton "literally personifies the failed establishment in Washington, D.C.," before ticking through a list of issues, such as immigration and Supreme Court nominations, where Trump has outlined what he characterized as a superior vision than that put forward by Clinton.

Trump touted Indiana's economic numbers during his lengthy introduction of Pence Saturday, which included shots at Clinton for her private email use and foreign policy positions.

Trump made light of Pence's decision to endorse Sen. Ted Cruz on the eve of the Indiana primary, calling it "the single greatest non-endorsement" he had ever received.

"[Pence] endorsed somebody else, but it was more of an endorsement for me," Trump joked.

Pence said he had received a call from Trump about becoming the Republican vice presidential nominee "last Wednesday." Trump was hinting as late as Thursday night that he had not yet settled on a running mate.

"I know from firsthand experience that strong Republican leadership can bring about real change," Pence said in his prepared remarks.

"Hillary Clinton must never become president of the United States of America," he added.