US Senator Mitt Romney, the lone Republican to vote to convict President Donald Trump of abuse of power following his impeachment, said on Thursday a Senate Republican investigation of Democratic presidential front-runner Joe Biden appeared politically motivated. Romney told reporters a probe of Hunter Biden, Joe Biden’s son, by Senate Homeland Security Committee Chairman Ron Johnson would be better pursued by the FBI or another federal agency “if there’s something of significance that needs to be evaluated.” Johnson is poised to issue the first subpoena in an investigation of Hunter Biden’s seat on the board of Ukrainian gas company Burisma when his father was US vice president. Hunter Biden’s role has been attacked as corrupt without evidence by Trump and congressional Republicans. “There’s no question but that the appearance of looking into Burisma and Hunter Biden appears political. And I think people are tired of these kind of political investigations,” Romney, a member of the homeland security panel, said. Trump was impeached on abuse-of-power and obstruction charges in the Democratic-led House of Representatives after he asked Ukraine to investigate the Bidens in July. He was acquitted by the Republican-controlled Senate. Democrats said Trump was trying to shore up his re-election prospects by targeting Biden. Trump continues to question Hunter Biden’s position at Burisma. “That will be a major issue in the campaign,” Trump told Fox News on Wednesday night. “I will bring that up all the time.” Republican Senate Majority Leader Mitch McConnell said Johnson had been looking into the matter before Biden surged in the nomination race this week. “Joe’s been around a long time. He knows that this sort of thing will be looked at when you become the likely nominee of your party,” McConnell told Fox News. Romney’s comments suggested Johnson could have difficulty getting his committee to approve a subpoena of Andrii Telizhenko, a former Ukrainian diplomat and consultant for Blue Star Strategies, a lobbying and consulting firm. Johnson alleges Blue Star sought to leverage Hunter Biden’s Burisma role to make inroads with the State Department. Johnson plans a committee vote on the subpoena next week. Romney declined to say how he would vote. With Republicans’ 8-6 majority on the panel, one Republican “no” could deadlock the subpoena question. Democrats have said Johnson’s investigation could aid disinformation efforts by Russia. Senator Gary Peters, the committee’s top Democrat, said he believes Republican members have qualms about the probe.