The purpose of our study is to identify the nature of the link between government spending and economic growth, in order to test the two theories of Wagner and Keynes, in the case of Romania. On the one hand, Keynes argues that public spending is an important tool to stimulate growth. On the other hand, Wagner says that increased public spending is a result of economic growth. We analyzed the long-term dynamics of the two time series through Johansen’s cointegration approach and, in the short term, with the help of Granger’s causality test. The obtained results do not indicate the existence of long-term cointegration vectors, but they support the double causality relation in the short term. Therefore, not only does GDP represent a Granger cause for government spending but also vice versa. Our results validate the liberal criticism of the state’s involvement in supporting economies. As the critics of the monetarist school said, the effect of multiplying government spending on national income is short-term. The long-term effect appears under the action of inflationary macroeconomic bottlenecks.