Bank stocks have been surging again over the past few days, as the outcome of the presidential election in France, as well as Donald Trump's vow to lower the corporate tax rate, is buoying investor sentiment toward the sector. Most recently, Trump reiterated his support earlier this week for lowering the corporate income tax rate from a high of 35% down to only 15%.Given that taxes impact a bank's net income in the same way operating expenses do, a substantial drop in the top rate as envisioned by Trump would translate into a meaningful increase in most banks' bottom lines.