WASHINGTON (BLOOMBERG) - US Secretary of State Michael Pompeo is ramping up his domestic appearances before overwhelmingly Republican audiences, raising criticism that he's going on the campaign trail for President Donald Trump by taking part in events that previous top US diplomats would have avoided.

Mr Pompeo will be in Wisconsin on Wednesday (Sept 23) to address the Republican-controlled state legislature in a speech billed as warning of the threat that states face from China's Communist Party.

He's following a string of Republican visitors to the battleground state including Mr Trump, Vice-President Mike Pence and Attorney-General William Barr.

The trip to speak in the state Mr Trump narrowly won in 2016 follows his participation in a "Values Voters" event Tuesday night, two speeches to a megachurch in Texas over the weekend and an address to the Republican National Convention while on a taxpayer-funded trip to Jerusalem last month.

The events have one thing in common: They give Mr Pompeo the opportunity to discuss administration foreign policy goals at home while also boosting Mr Trump - and his own standing with the president's political base ahead of a potential run for the White House in 2024.

"It's clearly unprecedented in the modern era and a clear violation of established norms," said Mr Daniel Weiner, deputy director of the Election Reform Programme at the Brennan Centre for Justice.

"Pompeo, for better or worse, has thrown that all out the window and engaged in more overt political activity than any secretary in recent memory."

Skeptics like Mr Weiner argue that while the speech isn't necessarily out of line, it fits a broader pattern in which the California native and former Kansas congressman has repeatedly strayed into politics while also serving his goals as secretary.

He has shown he's unusually willing to resort to partisanship in lauding the president while also trashing Democrats, all seemingly with an eye toward his future political ambitions.

As former Vice-President Joe Biden solidified his standing as the Democratic nominee, the 56-year-old Mr Pompeo mentioned him more and more frequently in criticising the Obama administration's policies, a break from past restraint against attacking predecessors' foreign-policy records so openly.

The secretary rejects accusations that he's engaging in domestic politics ahead of the Nov 3 election.

'COASTAL ELITES'

At Prestonwood Baptist Church in Texas last weekend, Mr Pompeo said he's "not allowed to do politics." He has scoffed at reporters who ask him about the trips, accusing them of being "coastal elites" who don't understand that he's trying to bring the department's message to the American heartland. He adds that his Christian faith is relevant because it informs the way he does his job.

A State Department spokesperson, speaking on the customary condition of anonymity, said Mr Pompeo's job is to lead the execution of Mr Trump's foreign policy priorities and communicating that message directly is an important part of his task.

Mr Pompeo is one of the few top officials remaining from Mr Trump's original Cabinet. After a year as CIA director, Mr Pompeo was tapped to replace Mr Rex Tillerson at the State Department in 2018, where he helped shield the president during the impeachment hearings by withholding witnesses and key documents from investigators.

Mr Pompeo's political approach to the job has rankled many staffers within the State Department, such as when he used a speech in Philadelphia to criticise the New York Times' 1619 Project on slavery and racism, saying it presented a false vision of America and betrayed a "Marxist ideology."

And while Mr Pompeo insists he's bringing his message to the American people, his strategy is notable for what's missing: Outreach to communities that don't explicitly support the president.

OWN GUIDELINES

In a move that critics called hypocritical, Mr Pompeo's Jerusalem speech contravened guidelines he personally approved that bar political appointees at the State Department from participating in political activity even on their personal time.

"The State Department reviewed this, it was lawful, and I personally felt it was important that the world hear the message of what this administration has accomplished," Mr Pompeo said at the time.

Critics said the speech may have violated the Hatch Act against partisan activity by a political appointee. Mr Pompeo's team said he had consulted with four sets of lawyers to make sure it was legal.

"Even if he's not violating the Hatch Act, Pompeo is doing things that look sketchy as hell," said Mr Nick Schwellenbach, a senior investigator at the Project on Government Oversight. "It's not just one-off here or there. It's a pattern."