Beverly Randles is the chairwoman of Club for Growth and has not formally announced her candidacy for the office yet.
Todd Abrajano, a Sinquefield associate who now serves as a spokesperson to the Randles' exploratory committee, said the donation will be used to help Randles come to a decision.
"She will travel across the state, we'll probably do some polling, all of that stuff costs money and so the donations the campaign, or exploratory committee receives between now and whenever she decides whether or not she will run will concern those purposes," Abrajano said.
If Randles chooses to run, she would be challenging republican incumbent Peter Kinder. Kinder has made no announcement regarding re-election, but if he chooses to run, he would be seeking a historic fourth term as lieutenant governor.
"As a lifelong Missourian who has had the opportunity to rise from humble beginnings to achieve numerous successes, my hope is that I can help others throughout our state realize similar opportunities to achieve their own goals," Randles was quoted as saying in her statement. "Over the coming weeks and months, I look forward to speaking with people all across our state about my vision for a better Missouri for all, and continuing to garner support for a potential campaign."
Randles' husband unsuccessfully ran for governor in 2012.
According to campaign finance records, the $1 million donation is the largest lump sum donated by Sinquefield to a single candidate since 2008. According to records, the billionaire also donated $870,000 to the only republican gubernatorial candidate in 2016, Catherine Hanaway, a former U.S. attorney and Missouri House speaker.
Sinquefield has given large contributions to other candidates in recent years, including more than $300,000 to help Attorney General Chris Koster, who recently switched to the democratic party, defeat two long-term democratic legislators in the 2008 primary.
Sinquefield also helped fund the Missouri Club for Growth, which campaigned for a successful constitutional amendment that gives lawmakers the ability to override the governor's spending decisions.
In a statement, Sen. Claire McCaskill, D-Missouri, slammed the Sinquefield's efforts to "purchase the loyalty of Missouri's elected officials."
"The question Missourians really need to ask is this - do they really want a government completely owned by one St. Louis billionaire?" McCaskill was quoted as saying in the statement.
Abrajano said McCaskill's comments strike him as "the height of hypocrisy."
"Over the course of the last few years, Sen. McCaskill has contributed, according to the St. Louis Post Dispatch, over $800,000 to democrats here in the state of Missouri," Abrajano said. "And so for her to make the claim that people who are contributing large dollars to candidates, it's just hypocritical. And she has continued over and over again to make large donations and so if Claire McCaskill wants to limit donations in the state of Missouri, she should start by eliminating her own."