The video shows Republican Bill Dix kissing the unidentified lobbyist.
In a statement issued following the announcement of Dix's resignation, Senate President Jack Whitver said he believed his fellow Republican "made the right decision for himself and for his district, but most importantly, I believe he made the decision in the best interest of his family".
The 18-year legislative veteran is married with three children, according to his statehouse biography.
Senate Democratic Leader Janet Petersen issued a statement raising the possibility that state policy had been affected by Dix's relationship with the lobbyist. The video shows the two kiss.
It's unclear whether Lindsey McCune remains a registered lobbyist for the League of Cities.
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According to multiple reports from Des Moines-area outlets, Republicans held the closed-door meeting, and after the meeting, Whitver released a statement about Dix's resignation.
One of the clients she represents, the Iowa League of Cities, issued a brief statement: "We are taking what we believe are appropriate actions, but because this is a personnel matter we can not comment further".
But by early afternoon, Dix had made the decision to end his Senate stay in the final year of his second term. Some called for Dix's resignation over the Senate's treatment of the case, which was settled for $1.75 million and resulted in the creation of a human resources manager position to handle harassment complaints down the road.
The Senate Republic Caucus will meet on Wednesday to elect a new leader. He became majority leader after GOP lawmakers took control of the chamber following the 2016 election. "After footing the bill for a $1.75 million settlement in Kirsten Anderson's lawsuit against Senate Republicans, Iowa taxpayers deserve nothing less", she said.
Dix, 55, is a third-generation farmer whose district covers Butler, Grundy, Hardin and Story counties.
Bill Dix talks about the Senate Republicans' efforts to address sexual harassment in their caucus on November 14.