WASHINGTON (Reuters) - U.S. Senator Mitt Romney will vote to allow a subpoena in a Senate Republican investigation of Democratic presidential candidate Joe Biden’s businessman son, Hunter Biden, his office said on Friday.

A day after Romney told reporters that the probe appeared to be political, a spokeswoman said the Utah Republican decided to back the subpoena after being assured that the records and witness interview sought would not create a public spectacle.

President Donald Trump, without evidence, has attacked as corrupt Hunter Biden’s role as a board director for a Ukrainian gas company while his father was the U.S. vice president. Trump said this week that he will use the issue against the elder Biden, a leading Democratic candidate to face Trump in the November election.

Senate Homeland Security Committee Chairman Ron Johnson, a Trump ally, is investigating the matter and will ask panel members to vote next Wednesday to subpoena records and an interview from Andrii Telizhenko, a former Ukrainian diplomat and consultant for the lobbying firm Blue Star Strategies.

Johnson claims Blue Star sought to leverage Hunter Biden’s Burisma role to make inroads with the State Department.

“Senator Romney has expressed his concerns to Chairman Johnson, who has confirmed that any interview of the witness would occur in a closed setting without a hearing or public spectacle,” Romney spokeswoman Liz Johnson said in a statement.

“He will therefore vote to let the Chairman proceed to obtain the documents that have been offered.”

A Johnson spokesman was not immediately available for comment.

Trump was impeached by the Democrat-controlled House of Representatives for asking Ukraine to investigate the Bidens. He was later acquitted by the Republican-led Senate, with Romney the only Republican voting to convict the president for abuse of power.

House Democrats alleged that Trump sought Ukraine’s help for his re-election campaign.

Johnson, who insists the investigation has nothing to do with the election, escalated the probe as Biden’s presidential bid surged in South Carolina and then the Super Tuesday primaries. Along with disclosing subpoena plans, the Wisconsin Republican said he would issue an investigation report in coming months.

Senate Majority Leader Mitch McConnell told Fox News this week that Hunter Biden’s Burisma role was worth examining. “Look, if you become the frontrunner you come under a lot of scrutiny, from the press, from both sides,” McConnell said.

Democrats have warned that the investigation could aid disinformation efforts by Russia.