CNN  — 

The Republican-led Senate on Tuesday failed to get enough votes to break a filibuster of Judy Shelton, President Donald Trump’s controversial nominee for the Federal Reserve.

But Senate Majority Leader Mitch McConnell, who had initially voted for the nominee, switched to vote against her, giving him the procedural right to bring her up for another vote in the near future. It’s not clear when that might happen. The final vote was 47-50.

At issue was a group of GOP senators who, like all Democrats, oppose Shelton’s nomination combined with a spate of GOP absences – some caused by potential exposure to Covid-19 – that are making the math tricky for Republican leaders as they try to get her confirmed.

Shelton has advocated a number of unusual policy ideas, including a return to the gold standard, which would link the US dollar’s value to the price of gold. America abandoned it in 1971. She has also attacked the Fed’s independence. In 2011, she called the central bank “almost a rogue agency.” This has been particularly problematic given the President’s continued criticism of the central bank, which is headed by another Trump pick, Chairman Jerome Powell.

Shelton was nominated for a Fed seat after the withdrawal of Trump economic adviser Stephen Moore following reporting from CNN’s KFile about derogatory comments he made about women. Moore later said he’d been joking.

Three Republicans already had already come out against Shelton – Susan Collins of Maine, Mitt Romney of Utah and Lamar Alexander of Tennessee – meaning she had a narrow path to confirmation to begin with.

But then Sen. Chuck Grassley, a Republican from Iowa, announced he would have to quarantine after potential exposure to Covid-19 and miss the vote – his first missed vote in 27 years. He joins Florida Republican Sen. Rick Scott, who announced Saturday he would be away from the Capitol for the same reason.

Further complicating the count, Alexander said that because of a family situation he would not be in the chamber to cast his vote against Shelton.

McConnell’s move meant Grassley and Scott could be back to vote for Shelton but with the Senate away next week for Thanksgiving, McConnell would likely not be able to schedule that until the following week.

But by that point, Sen.-elect Mark Kelly, a Democrat who won a GOP seat in the special election in Arizona, is expected to be sworn in, meaning there would likely be one more Democratic “no” vote standing in Shelton’s way.

“There is a little bit of a complicated factor in the Arizona seat,” said Senate Majority Whip John Thune, a South Dakota Republican.

CNN’s Anneken Tappe contributed to this story.