In a political earthquake, one of the most powerful Republicans in one of America's most closely-watched swing states is calling it quits.According to Civic Media's Dan Shafer, Wisconsin Assembly Speaker Robin Vos announced on Thursday in a speech at the beginning of the assembly floor session, “I will not be running for re-election in November.”In the announcement, Vos said that his recent heart attack was a sign from God to retire.Vos has been a titan of Republican politics in Wisconsin, holding the speakership of state assembly for over a decade, and for most of it presiding over a heavily gerrymandered body that elected heavy majorities of Republicans even when a majority of voters backed Democrats. After GOP firebrand Gov. Scott Walker was defeated for re-election in 2018, he effectively became the most powerful Republican in the state, often thwarting Democratic ambitions on key legislation.After 2020, he found himself in the middle of bruising intraparty fights, including a clash with a former state judge turned election conspiracy theorist he himself had hired to probe election fraud.Additionally, after voters elected a liberal majority on the state Supreme Court that overturned the state's legislative gerrymanders, Vos' power became less certain.