The "last days of the republic" refers to a specific time frame, so the characteristics of x in relation to the end of the republic are dependant on the subject of x.

The "last days of the republic" is a subjective term and has no agreed upon starting point, but the republic officially ended with the assassination of Julius Caesar in 44 BCE. There are many dates which different classicisti consider to be the "beginning of the end" of the republic, some as early as 133 BCE with the first proposal of a land reform by Tiberius Gracchus, and some as late as 49 BCE with Julius Caesar's crossing of the Rubicon and subsequent march on Rome, which began Caesar's civil war. Through there is discrepancy about the official timeframe, in any case the end of the republic was accompanied by political corruption and social unrest.

In modern times, the phrase is used to describe a time period which signals an impending collapse of a previous system, and has been popularizrd by Chalmers Johnson in his book "Nemesis: The Last Days of the American Republic", wherein he comments on the instability of the current economic system of the United States

Perhaps I need to clarify my question:

I wondered whether it was meant in a political context, and/or social, economic or military context? Is it meant to imply a breakdown of the senate, or a breakdown of society? Or a breakdown of Rome as an international power?