WASHINGTON — When Georgia’s governor picked Kelly Loeffler, a little-known Atlanta businesswoman, to fill the state’s vacant Senate seat late last year, her vast personal wealth and ability to fund her own campaign were top selling points for Republicans.

Ms. Loeffler, whose husband runs the New York Stock Exchange, pledged to put $20 million of her own fortune toward holding onto the seat in a special election this November. She bought a private plane to fly to and from Washington. And she blanketed televisions with ads highlighting her American-dream-style rise from a humble family farm to the pinnacle of high finance.

Now, amid an economic crisis brought on by the coronavirus pandemic, Ms. Loeffler’s wealth is threatening to become a major political liability. She is facing questions about whether, in actively trading millions of dollars in stocks over the past couple of months, she and her husband have profited off the crisis based on information she received through her position as a senator.

Ms. Loeffler, who adamantly denies wrongdoing, is one of several senators whose investments have come under scrutiny in recent days. The Securities and Exchange Commission and the F.B.I. are investigating the decision by Senator Richard M. Burr, Republican of North Carolina, to liquidate most of his portfolio in mid-February before the markets collapsed, a review that a person familiar with it said would most likely include multiple other lawmakers.

But Mr. Burr is retiring. The fallout for Ms. Loeffler, a political newcomer up for election in just seven months, is potentially much more damaging. She faces a formidable challenge not only from Georgia’s resurgent Democrats but also from Representative Doug Collins, a Republican and vocal defender of President Trump who has refused to drop out of the race despite pleas from party leaders.

Democrats and Mr. Collins are both working to try to transform what just months ago promised to be one of Ms. Loeffler’s strongest political assets — her financial acumen — into a fatal flaw.

“There are a lot of people angry at a person who has possibly used nonpublic information to benefit themselves personally while telling Georgians it was all going to be OK,” Mr. Collins said in an interview on Wednesday, referring to public statements Ms. Loeffler made weeks ago playing down the threat of the virus.

A former financial executive, Ms. Loeffler, 49, calls the charges preposterous, particularly for someone schooled in insider trading laws. Her investments, like her husband’s, are handled by outside financial advisers, she has said, and those advisers alerted her about the transactions in question only well after they were made.

“These accounts are managed by third-party entities,” Ryan Mahoney, a spokesman for Ms. Loeffler’s campaign, said Wednesday. “She doesn’t have any oversight, she doesn’t have any discretion. These are simply attacks during a very difficult time in America and in Georgia.”

The controversy stems from millions of dollars worth of trades made in the name of Ms. Loeffler and her husband in late January after she attended a private, senators-only briefing on the virus with top government health officials. At that time, as the disease was raging in China, few Americans realized its potential to become a pandemic.

The stocks sold, including Exxon Mobil, Ross Stores and AutoZone, later lost a significant amount of value, prompting accusations of insider dealing by critics who argued that the timing of the transactions could not be a mere coincidence. But there is no evidence that senators received any significant nonpublic information in the briefing.

New public disclosure forms filed with the Senate late Tuesday showed that stocks worth millions of dollars owned by Ms. Loeffler and her husband continued to be actively traded in February and early March, as the markets began to sharply decline. In some cases, the couple saved money they might have otherwise lost by selling, but in aggregate the trades do not appear to have made a substantial impact on their net worth, which exceeds $500 million.

Ms. Loeffler is married to Jeffrey Sprecher, the founder and chief executive of Intercontinental Exchange, or ICE, a publicly traded company whose crown jewel is the New York Stock Exchange. Ms. Loeffler was the chief executive of Bakkt, an ICE subsidiary, before accepting the Senate post. She is also the co-owner of Atlanta’s W.N.B.A. team, the Dream.

The legal risk to Ms. Loeffler is probably low, and there is not yet any evidence that she is under federal scrutiny like Mr. Burr. The Stock Act makes it illegal for members of Congress to trade on nonpublic information they encounter in their work. But no one has ever been prosecuted under the law, and if it is as Ms. Loeffler describes, her financial arrangement would insulate her from charges, experts said.

Still, questions about her investments could do lasting political harm to Ms. Loeffler at a time when many Americans are on edge and concerned about the devastating financial toll the crisis has taken on them.

“She may not have any kind of legal problems, but it does indicate she comes from a very different world than 99.99 percent of Georgians,” said Charles S. Bullock III, a political-science professor at the University of Georgia.

Mr. Bullock said the stock trades — particularly if they become an explicit target of a federal investigation — could “plant the seed of doubt in some voters’ mind: Can a person who is this wealthy represent your concerns, as, say, a family that has lost its job because of this pandemic?”

Even before the virus began ravaging the United States, Mr. Collins had been trying to use Ms. Loeffler’s wealth against her, putting together hard-edge digital ads making light of her expensive clothing and private plane to paint her as out of touch with ordinary people.

“From the public perspective, people require us, rightly or wrongly, to look after their interest, not our own,” Mr. Collins said on Wednesday.

Democrats, who see the seat as a potential pickup opportunity at a time when their party is making gains in the state, have made an aggressive push to capitalize on the sales, as well. American Bridge, a liberal super PAC, cut a digital ad tagging Ms. Loeffler as “Crooked Kelly.”

“Georgia hospitals are at their breaking point and Georgians are losing their jobs, their businesses and their retirement savings, yet apparently all Senator Loeffler could think about was her stock portfolio,” said Helen Kalla, a spokeswoman for Senate Democrats’ campaign arm.

Polling commissioned by Mr. Collins’s campaign shows a sharp uptick in those viewing Ms. Loeffler unfavorably in the days after initial reports in March about her January stock sales, though there have not been public surveys that confirm the findings.

Republicans involved in the race played down the long-term political risk to Ms. Loeffler. They pointed out that Republican voters had eagerly embraced Mr. Trump’s wealth, despite the complications it had created, and argued that as long as Ms. Loeffler continued to explain her unusual financial arrangements, they would not punish her either.

Ms. Loeffler’s allies have tried to turn the attacks on her against her rivals. Jesse Hunt, a spokesman for Senate Republicans’ campaign arm, said on Wednesday that Democrats were spreading “false attacks” based on shoddy journalism. He took aim at Mr. Collins, as well.

“What’s shocking is there’s a so-called Republican perpetuating liberal lies against another Republican during a global pandemic because his feelings are permanently hurt,” he said.

Katie Benner contributed reporting.