Dublin South West is a perfect place to test the pulse of the nation. During the 2011 general election, RTE made an award-winning documentary called Dogfight that largely consisted of voters hurling abuse at the constituency's doomed Fianna Fail candidates.
One man summed up his feelings by shouting after Conor Lenihan: "If I had the money, I'd buy you a ticket to Afghanistan."
Next Friday's by-election is likely to confirm that the people of Dublin South West are still mad as hell. This time, however, they have Enda Kenny's government squarely in their sights.
With disgust for the establishment parties running high, it looks as if the capital is leaning left - and that will make it all the harder for Fine Gael to recover from the scandals that have dogged them throughout 2014.
Michael Noonan's budget is now barely a week away, but this week's events should once again prove the old saying that all politics are local.
On the same day that Dublin South West goes to the polls, another by-election in Roscommon-South Leitrim will likely show up Enda's (left) problems with rural Ireland too.
Meanwhile there is the little matter of that infamous Seanad by-election, which may leave the Taoiseach more red-faced than ever if his crony John McNulty manages to squeeze through.
The Dublin vote, however, has a particular symbolic importance. In 2011, three of the four Dail seats here went to government candidates.
On Friday, it would be a miracle if either Fine Gael or Labour came within an ass's roar of victory.
The explanation is simple. Every canvasser knocking on doors agrees that water charges have put a large dent in the government's popularity.
This is why Sinn Fein's Cathal King is the overwhelming favourite (at 1/16 with one bookmaker) to win Friday's contest.
His only serious rival seems to be the former Socialist Party MEP Paul Murphy, currently languishing at 6/1. Both men are loudly opposed to water charges - and both seem to have struck a chord with voters.
The battle for Dublin South West's left-wing vote has already got ugly. On Saturday, Paul Murphy was outraged by a fake Facebook post that appeared to show him lying about Sinn Fein's policy on water charges.
The Shinners were caught bang to rights and were shamed into a public apology before the day was out.
Barring a huge upset, Dublin South West is about to become the most left-wing constituency in Irish political history, with two Labour TDs and probably two Sinn Fein deputies as well.
If Fine Gael dismiss this as a protest vote with no long-term consequences, they will only be fooling themselves.
Just look at May's European election in Dublin, where an incredible 77pc opted for anti-government candidates.
This should have been a massive wake-up call - because Dublin is the cockpit of any general election and a government that loses the capital will lose the country too.
Enda Kenny has just endured a miserable fortnight.
It still looks a safe bet that the Taoiseach's losing streak will continue for at least another week.