What if someone becomes President of a country by fraud, corruption, rigging elections, stealing votes, buying off votes, bribes, destroying the opposition’s votes, etc. etc., does Romans 13 still apply for such a usurper? Would it not be allowable and a duty to seek to overthrow his government?

Such may not be the case for the USA, but it is definitely the case in Nicaragua right now, and other countries.

There is so much Irony in this story.  Daniel Ortega, elected pres of Nicaraqua was the Sandinista dictator that overthrew Somoza in the late 70's early 80's, resulting in Commander Zero and his somosista "Contra" rebel organization that he U.S. funded through illegal weapon sales via Israel to Iran as well as CIA cocaine trafficking via Manuel Noriega (remember when they shot down Eugene Hasenfues (cia operator) with all that blow on board in nicaragua?  I do, because I was a Marine 0331 who was part of taking him down late December 1989)  They finally return to democracy with a peaceful election of Violletta Chomorro.  Fast forward Danny boy has what by all accounts has a sincere conversion/reversion to his Catholic faith and gets actually elected.  Don't know much about how corrupt or usurped the govt. is.  I'd say, like all governments, there is more or less corruption wherever you go, especially what we are learning about our deep state.   No opinion on this, but it's link to a significant era in my life got my attention,.