Angel’s phrase here—Marchemos, y yo el primero, por la senda constitucional—is an almost perfect reproduction of the phrase Marchemos francamente, yo el primero, por la senda constitucional uttered by Fernando VII when he finally found himself forced to accept—temporarily at least—the Constitution. Given that, and Angel’s own political orientation, it comes across as being both bitter and ironic. A short but very stinging Galdosian portrait of this monarch can be found in La Fontana de Oro (1870). It is perhaps worth noting in passing that one of Galdós’more famous tag-lines—francamente, naturalmente (frankly, naturally—constantly voiced by the character of Ido in Fortunata and Jacinta (1886-87), and earlier by the narrator himself at the end of The Bringas Woman (1884), may stem in part from Galdós’ disgust at Fernando’s hypocrisy.
Six “naturally” referenced quotes are by him just in the subchapter he’s introduced (Volume One, Chapter 8, sub-chapter 4). I’m not sure why Galdós puts the word in this character's mouth so often. My best guess is that Ido is both truthful and a fraud, a paradox the author brilliantly depicts, although he's not willingly a hypocrite. Regardless, I love little tidbits like this.