Why do you think it is important for politician parties to act as watchdogs?

It's important because the party that lost the election for president watches the actions of the party in power for mistakes or misuse of power.

Currently, as of february 2016, an american traveling in france would be by the exchange rate. the weakness of the euro and the strength of the us dollar means that items in france cost less to an american than they otherwise would. of course, if this trend reverses and the us dollar weakens and the euro strengthens, such as was happening in early 2008, an american traveling in france would have an adverse experience because items would cost relatively more.